I would think that a hard limit would be bad, and if you are paying XP for it you won't want to trade out.
Luckily, you don't have to guess. We can playtest it!

I would think that a hard limit would be bad, and if you are paying XP for it you won't want to trade out.
Path of the Spider {Poison said:0 - Venom Handler - Gain Soak 2 vs Poison for 1 minute
1 - Lesser Venomed Strike - Your blade drips with a weak poison that adds 1d6 poison damage to your attacks. This effect lasts for one minute.
2 - Ensnare - Target 1 Medium or smaller creature within 30' and roll Mag vs Agi, if successful the target is wrapped in a strong silken cocoon and will begin to suffocate. It, or its allies, can attempt to break free by spending a full round and pass a STR check vs 10. This effect lasts for 1 minute
4 - Spider Climb - You gain Spider Climb for 10 minutes
5 - Venomed Strike - Your blade drips with a poison that adds 3d6 poison damage to your attacks. This effect lasts for one minute.
6 - Spider Shape - You transform into a Large Monstrous Spider, gaining a Str of 16 (9d6), Agi of 6 (4d6), and End of 10 (6d6). You also gain natural armor with a SOAK of 10, a Climb speed of 14 (70'), a poisonous Bite (9d6: 4d6 stabbing and crushing damage: venom 6d6 vs End; 2d6 poison), a Web attack (4d6: range 6; restrains), low-light vision, and 8 legs. This form lasts for 1 hour.
7 - Web - Cast a web 30' away and Ensnare Enormous creatures or smaller in a 20' radius. The STR check to break free is vs 16.
8 - Greater Venomed Strike - Your blade drips with a strong poison that adds 4d6 poison damage to your attacks. This effect lasts for one minute.
10 - Phase Spider Shape - As Spider Shape, your attacks can ignore SOAK from armor and can affect incorporeal creatures.
Path of Bones {Undead} said:0 - Shambling Skeleton - Summon a basic Skeleton to serve you as best it can. It will defend you, but dissipates after 1 minute
1 - Lesser Skeletal Armor - Garb yourself with a garish armor made of bones, Gain SOAK 2
2 - Monstrous Skeleton - Summon a Monstrous Skeleton to server you as best it can. It dissipates after 1 minute.
3 - Skeletal Warrior - Summon a basic Skeleton, equipped with LongSword and ChainMail (Soak 8). It will defend you, but dissipates after 1 minute.
4 - Skeletal Armor - Garb yourself with a garish armor made of bones, Gain SOAK 4
5 - Flaming Skeletal Warrior - Summon a Skeletal Warrior that deals an additional +1d6 Fire damage, has an increased Speed +4, and ignites flammable objects that it touches.
6 - Monstrous Skeletal Warrior - Summon a Monstrous Skeleton that has an increased Speed +4 and adds +2d6 fire damage to its attacks. It will defend you, but dissipates after 1 minute.
7 - Skeletal Squad - Summon 5 Skeletal Warriors to fight your battles. They dissipate after 1 minute.
8 - Greater Skeletal Armor - Garb yourself with a garish armor made of bones, Gain SOAK 16
9 - Flying Flaming Skeletal Warrior - Just what it says, this guy Flies!
10 - Elite Skeletal Squad - Summon 2 Monstrous Skeletal Warriors to fight your battles. They dissipate after 1 minute.
Skeleton said:Medium Brainless Undead; level 0 (XP)
STR 5 (3d6) AGI 2 (1d6) END 5 (3d6)
INT 1 (1d6) LOG 1 (1d6) WIL 1 (1d6) CHA 1 (1d6)
INITIATIVE 1d6
PERCEPTION 1d6
SPEED 6 (30'); CLIMB 4 (20'); FLY - (-’) JUMP 4'/4'
CARRY lb
HEALTH 18
DEFENSE 10
MENTAL DEFENSE 2
RESISTANCES Immune to Charm and Compel
Weapon Resistance: Takes 1 point of damage per Die from Piercing damage
VULNERABILITIES Cold I
NATURAL DAMAGE 1d6
Claw (x2) 4d6 (1d6 slashing)
EXPLOITS
SKILLS Claw II
EQUIPMENT none Skeletons are the animated bones of the dead, mindless automatons that obey the orders of their evil masters. Skeletons attack until destroyed.
Monstrous Skeleton said:Large Brainless Undead; level (XP)
STR 12 (4d6) AGI 8 (3d6) END 11 (4d6)
INT 5 (2d6) LOG 3 (2d6) WIL 5 (2d6) CHA 1 (1d6)
INITIATIVE 3d6
PERCEPTION 2d6
SPEED 12 (60'); CLIMB 6 (30'); FLY - (-’) JUMP 19'/19'
CARRY lb
HEALTH 32
DEFENSE 23 (SOAK 10)
MENTAL DEFENSE 10
RESISTANCES Immune to Charm and Compel
Weapon Resistance: Takes 1 point of damage per Die from Piercing damage
VULNERABILITIES Cold II
NATURAL DAMAGE 4d6
Claw (x2) 6d6 (4d6 slashing)
Knockdown Strike 5d6 (4D6 and target is forces prone)
EXPLOITS Knockdown, Opportunistic Stomp
SKILLS Tactics, Claw II, Run
EQUIPMENT none Skeletons are the animated bones of the dead, mindless automatons that obey the orders of their evil masters. Skeletons attack until destroyed.
Path of the Eye (Light) said:0 - Cast Vision - Select a point within 800' and concentrate to view a 20' radius from that point. Creatures within view may notice that they are being observed magically if they pass a WILL vs your Magic check. The spell ends when you cease concentrating or 1 minute, whichever is less.
1 - Magic light - Touch an object to transform it so that it shines with a bright light in a 20' radius {and dim light an additional 20'}. This light lasts for 10 minutes.
2 - Darkvision - You Gain Darkvision with a range of 60' for one minute
3 - Blindsight - You gain the ability to see invisible creatures within 30'. This effect lasts for 10 minutes
4 - Omnivision - You gain the ability to see through solid objects within 30' and ignore all forms of concealment except for darkness. This effect lasts for 10 minutes
5 - Shared Darkvision - Select up to {your LOG attribute} creatures within 10' of you to grant darkvision with a range of 60'. The vision lasts for 10 minutes
6 - Shared Blindsight - Select up to {your LOG attribute} creatures within 10' of you to grant blindsight with a range of 30'. The vision lasts for 10 minutes
7 - Shared Omnivision - Select up to {your LOG attribute} creatures within 10' of you to grant Omnivision with a range of 30'. The vision lasts for 10 minutes
8 - True Sight - Gain Darkvision, Blindsight, and Omnivision with a range of 60'. The vision lasts for 10 minutes.
9 - Stalkers Alarm - During the next week, the first invisible creature to approach within 30' triggers a Blindsight spell that targets you, immediately revealing the creature.
10 - Banish the Dark - During the next week, if you enter Magical Darkness you immediately benefit from a casting of Darkvision that lasts for 10 minutes
11 - Shared True Sight - Select up to {your LOG attribute} creatures within 10' of you to grant True Sight with a range of 60'. The vision lasts for 10 minutes
Path of Might (Earth said:0 - Empower - Gain a bonus die to STR attribute checks, to include STR based damage, for 1 minute. You can be targeted by spells that affect the Earth Element.
1 - Weaken - Target a creature within 10' and pass a Mag vs Mental Def, that creature suffers a 1d6 penalty to STR attribute checks, to include STR based damage, for one minute.
2 - Brutal Slam - Select a weapon to enhance, that weapon's attacks ignore up to 4 points of SOAK.
3 - Tough Skin - Gain SOAK 4 for 10 minutes
4 - Laborers Strength - Gain an effective STR score of 20 {5D6} for the purposes of your Carry capacity {920 lbs} and opposed STR checks.This STR does not change your STR related damage. This strength slips away in 10 minutes
5 - Strength of a Hill Giant - Gain +5 to your STR attribute for one minute. This may change your DEF, Speed and STR dice.
6 - Enlarge - Your stature grows, gaining the next size increment. You gain +1 to Speed,-2 to DEF, and are Empowered. If your new size is bigger than Medium you also gain +5 SOAK and a REACH of +1. This effect lasts for 1 minute.
7 - Shrink - Touch a creature and pass a Mag vs END check to reduce the creatures size by 1 or 2 categories. For each category they will lose +1 Speed and gain +2 DEF. They may lose SOAK and Reach gained by their larger size. This effect lasts for one minute.
8 - Shared Strength - Select up to {your LOG attribute} creatures within 10' of you to grant the 'Strength of a Hill Giant'.
9 - Brute Squad - Select up to {your LOG attribute} creatures within 10' of you to grant Enlarge.
10 - Become the Turtle Bear - For 10 minutes you are Empowered, gain +8 SOAK, and can select a weapon to enhance with the ability to ignore up to 8 points of SOAK.
11 - You are the Brute Squad - Gain the benefits of both Enlarge and Strength of a Giant for one minute
Yup, the Shrink is specifically a MAG vs End in the current iteration since it is a physical change of the target. That means that targeting the big brutes with this spell is harder {as I think it should be} whilst having it target Mental Def {as it is a magical attack} would make big brutes an easier target.
Yes, but would a shield apply?