3catcircus
Adventurer
I think the ability to take two actions in rapid succession (ie without the opponent having the opportunity to react to the first action before you can take the second) carries the potential to be very powerful in action. Let's powergame it (and this takes the matter to an absurd, if logical, extreme).
I'm a glass cannon. The opponent will kill my character with one blow. He's that powerful. I can do some decent damage, but I need two or three hits to really turn the tide. My teammates are tanks, and can tie the opponent down, but can't really hurt him, so they can only prolong the inevitable. My initiative is 14, including -3 from a medium load which I can eliminate by dropping a sack of rocks (carried for just such an occasion). The Big Bad's is 15.
Round 1: Init 15, Big Bad swings on one of the Tanks
Round 1: Init 14: drop sack of rocks; charge the Big Bad (since my bag of rocks is more than one move action away)
Round 2: Init 17; withdraw and pick up big bag of rocks
Round 2: Init 15: Big Bad can swing on one of my teammates, chase after me (and suck up attacks of opportunity from my teammates - I won't be within a single move action, so he can't attack unless he charges), or delay/ready until I come back. From here, I either:
(a) If Big Bad keeps swinging on my teammates, drop rocks at 14 to charge, then retreat at 17 next round. Wash, rinse, repeat.
(b) If Big Bad delays, the situation has reversed - since he never acts, my teammates eventually beat him down.
(c) If Big Bad charges, all my teammates use trips, bull rushes, etc. as their AoO to slow him down - once one succeeds, they use normal melee attacks to get some extra damage in
Accessing two actions with no retaliation seems potentially powerful to me.
The problem, though is you can't charge on round 1 and end up with an Init 17 on round 2 - the full-round action means you'll finish it at the same point in time in round 2, so you won't gain the benefit of lowering your encumbrance until round 3. Likewise, withdraw is also a full round action, and picking up that bag of rocks is a move action.
BB could chase you on round 2 and you'd be stuck going after him in initiative order. If he doesn't and continues beating on someone else, on round 3, you could charge him (going first), but then you'd have to wait until round 4 to withdraw, pick up the rocks on round 5, go later in initiative order on round 6 to drop the rocks and charge, go at the same (lower init) in round 7, and then go earlier in round 8 to wash, rinse, repeat. You are losing the chance to attack basically every other round by doing this instead of treating the house rule the way it is intended - to reward players who take a risk by dropping items they might need in the middle of combat/penalize players who choose to carry a ridiculous amount of gear into combat and expect to fight as well as someone who isn't so weighted down.
What inspired me was watching some documentary about airborne troops. They shuffle to the airplane like pregnant yaks and during landing, they can detach some of their gear to fall the last couple of feet on a lowering line, so that when they hit the ground, they have better agility and mobility. Likewise, regular infantry don't carry their duffels onto a battlefield. In fact, there is an interesting article on globalsecurity.org that pretty much lays out some recommended loadout configurations:
Fighting load = 39.6 lbs. - basically weapons, ammo, armor, map/compass/writing stick, first aid, and water.
Fighting light = 59 lbs. (worn plus assault pack) - add food, more ammo, some clothes, and some small gear.
Approach march = 72.9 lbs (worn plus ruck sack) - more clothes, more food/water, more small gear, tool kits
Everything = 95 lbs.
I'd equate this for D&D to:
Fighting load = weapons, armor, 1 load of ammo, spell components, 1 potion of cure wounds, waterskin, light source.
Fighting light = add food, another load of ammo, 1-2 small magic items (rod, potion, scroll) or alchemicals.
Approach march = add additional magic items (cloaks, boots, weapons, etc.) and other miscellaneous stuff.
Really - this means that you take only what you need immediately (within 1 round) during combat with an option to add additional stuff for specific scenarios, but the 12 potions of cure light wounds, goggles of minute seeing, and 14 volume matched-set spell books stay in the area of the dungeon that you've secured already.