Dretch punting can be turned on/off just like friendly fire.
And I'd like to see your proof for "[such and such largely unused cheat] is necessary for balance". If not for that, it's about time to lock this thread.
I had mentioned about dretch punting, but I do not promote the idea of simply turning g_dretchPunt off, but instead to provide an alternative way of TKing dretches since TK to get a builder is such a widely used practice and is considered OK. Perhaps by allowing the dretch itself to choose whether their client-side dretch punting is on or off, such as, perhaps a cg_dretchPunt cvar. This would be similar to cg_unlagged in the sense that you can turn it off on the client side. This would be wonderful for balance.
As for using /team s for gaining a builder, as tremulant mentioned, the patch proposed on the bug tracker fixes this particular minor "problem" (but does not handle real abuse), but really if it means that much to everyone that a dretch isn't considered as having committed suicide by /team s, why not instead penalize by deducting credits in the amount the player is worth. This IMO would be more fair as the 30 sec timer does absolutely nothing for people who actually use it as a cheat to escape death.
As for your request for proof, read on below to the third point in my answer to SirDude. Balance is implied here since there is clearly an OBVIOUS advantage for humans.
And last but not least, although I do not exactly agree with the 30 second timer for /team switching, all I would like is for the RULES to CLEARLY state that using /team s to gain a builder is NOT OK, and is punishable with a kick or ban. This way, everyone will be clear and whoever else sees it happening can report it or at least alert the player who is doing it that it is wrong in case he doesn't know it.
are you forgetting that that 30 sec time will...
someone might take your player slot on humans OR humans will still have more players then aliens and you will be forced to join aliens!
why fix it?
a better question is why not fix it?
Firstly, it doesnt take 30 secs for someone to take up your slot. (EDIT: Consider for a moment that this so-called cheat will most likely be used when the team is on the losing side (or apparently so). A lot of players leave their team once they feel that all hope is lost. In this sense, you might actually gain a free slot rather than lose it).
Secondly, it is not a fix as it only prevents it from being used for 1 purpose only, whereas other purposes of /team s should be more seriously viewed as a cheat.
Thirdly, using /team s to gain a builder to my knowledge has only ever happened when aliens are being pounded and there is no overmind, only eggs. Almost all the players are dretches and as you know there is no way to TK a dretch. There is a CLEAR advantage here for humans caught in a similar situation (no arm or rc and most players on the team spawned as a rifle instead of a CKit).
In conclusion, the proposed "fix" really does nothing useful.