While I agree that its kind of silly that you should use anything other then
CARRY parts to transport energy/resources, this change is just a pretty crude fix to treat the problem, rather then actually cure it.
The core issue at hand here, is the fact that
CARRY doesn't hold enough energy relative to the cost of the other creep parts. In essence, the energy content of a single
HEAL part is equal to the carry capacity of 5
CARRY parts. I don't think nerfing recycle is the proper way to fix this imbalance, but rather adjusting either part costs or carry capacity is the more proper fix.
Additionally, applying a flat 30% tax on creep recycling feels like a sudden departure from the way other other game mechanics are balanced (e.g. creep renewing cost/tick time), which is that of a near zero-sum game. With this change, the instant I spawn a creep (regardless of purpose), I lose 30% of the energy cost of that creep instantly, which I don't think makes any sense.
The idea that you get less energy back for 'used' creep parts is already implemented as is, i.e. older creeps return (proportionally) less energy based on TTL. So I don't really buy that as justification for adding this recycle tax.
I think being able to fluidly convert between raw energy and creep parts is a really nice design choice, that shouldn't be abandoned simply b/c players are using creep parts in ways they weren't originally intended. It's also not like there aren't other cost factors the come into play when turning energy into creep parts (i.e. spawn time/pressure, CPU costs, etc.), so there are still interesting optimization choices to be made on the part of the player.
just my 2c