I think that my basic scheme will accomplish those goals, tbh.
Basically:
A weasel would be a scout, with a climb speed, keen senses, a “harrying attacks” action that does small dmg but sets up the ranger or else a special help action or a scouting action (survey the area), and a quirk like Sneak-thief which gives it sleight of hand and stealth proficiency.
I like where you're going with this. The below is for a different system I'm creating, but perhaps there's an ability to cannibalize some of these ideas to a D&D campaign.
(For context, tier level is like regular level, and every 3 tier levels you move into a new chapter. Each time you gain a tier level, you choose another maneuver to learn).
Packmaster
When you choose this specialty, you gain an affinity for
beasts, preferring their company to intelligent humanoids. You have learned the skills to train and incorporate creatures into your pack, with you as the alpha. Whether you lead them through a bond of friendship or power, they will follow your lead and commands.
You also gain one beast to become part of your pack. This creature’s level must be no higher than your tier level. As you level up, you can include more beasts to your pack, as long as the total levels do not exceed your tier level. 0 level beasts are considered ½ level for purposes of determining quantity.
If one of your beasts dies, you may summon another by spending an 8-hour ritual calling it. The available type of beasts will be determined by the area and habitat in which you perform the ritual in. That is, if you perform a ritual while deep underground, you may attract burrowing creatures instead of flying creatures.
Commands: You can spend 1 AP to issue a command to one beast. This beast will follow the command to the best of its ability. If you do not issue a command, the beast will react in the most natural way it would based on the scenario. You may issue commands to multiple beasts on your turn, with each costing 1 AP.
Pack Details
Your beasts will use the stat blocks as described in the Bestiary with the following adjustments:
- When making any Challenge roll, their dice pool will consist of 1PD, where the PD equals your proficiency die type. I.e., if your PD is a d10, then your beasts would use 1d10 when making attack rolls, ability checks, and determining the difficulty TCN their opponent must succeed against for things like poison or other special abilities.
- The creatures part of your pack resolves their actions during your turn.
Chapter 1 Maneuvers
Beast Tongue: You gain the ability to understand basic communication with beasts. They understand your commands but remember that their intelligence remains, so the form and content of their communication back to you will be simple regarding how they perceive the scenario. Smells and sounds will typically dominate descriptions rather than visual cues that we humans like to describe things with.
Cunning Strike: When a beast under your command makes a successful attack roll and attacks from surprise or behind, it may apply your Cunning Strike damage rather than you this turn. Only one beast can apply this damage per turn.
Defensive Beasts: Each of your beasts gain a +1 bonus to its DEF
Efficient: Each of your beasts gain a +1 bonus to its AP.
Pack Master: The total levels of beasts you can have in your pack now equals your tier level +1.
Chapter 2 Maneuvers
Defensive Beasts II: (Requires: Defensive Beasts). Each of your beasts gain an additional +1 bonus to its DEF.
Enchanted Claws: Natural attacks from members of your pack are considered magical in terms of overcoming resistance and immunities.
Intercept: If you are within 5 feet of an attacked member of your pack, you can spend 5 vigor and move that attack to yourself as a response, as if the attack was on you instead.
Recovery: Spend five vigor (AP: 2) to touch a pack member within 5 feet of you to remove any one negative condition afflicting that creature.
Specialist: The dice pool for Challenge Rolls that your beasts use increases to 2PD rather than 1 PD.
Chapter 3 Maneuvers
Beast Flurry: (AP: 5) Reduce the AP costs of attacks of all members of your pack by 1 (minimum 1) until the start of the next round.
Hinder: Your beasts do not attack. Instead, they spend 4 AP to hinder a target they can reach. For each beast hindering a target, its DEF is reduced by 1 until the start of your next turn.
Overwhelm: If you and your pack all attack the same creature this turn, each of you adds a bonus die to your attack Challenge Rolls equaling 1 + your Chapter level.
Pack Master II: (Requires: Pack Master). The total levels of beasts you can have in your pack now equals your tier level +3.
Telepathy: You can now communicate telepathically with members of your pack up to a range of 1 mile.
Chapter 4 Maneuvers
Efficient II: (Requires: Efficient). Each of your pack members gain an additional +1 to their AP pool.
Monster Hunter: You can have monsters as part of your pack. The monsters must either share your alignment or have a neutral/unaligned alignment.
Pack Form: (AP: 6) Change your form and all equipment carried into that of a creature type that is a member of your pack. This change lasts until your vigor is reduced to zero or you spend another 6 AP to change back.
Pack Master III: (Requires: Pack Master II). The total levels of beasts you can have in your pack now equals your tier level +4.
Specialist II (Requires: Specialist). The dice pool for Challenge Rolls that your beasts use increases to 3PD rather than 2 PD.
For additional context, this is an example beast on how they are structured. So a level 12 Packmaster could have up to 3 (total levels = 12) dire wolves as part of their pack, unless they've chosen Pack master, where they could have 4 (total 16 levels).
or 16 giant rats!