Now the ups and downs as I see them :
1. It's a grey area... when is somthing an exploit. I would say a good rule of thumb is that if you're using uncapped sysvars to kill a bot faster than you should be able to, then it's an exploit.
But there's probably other situations, personaly I think raping alge is an exploit (But sexrepro is only allowed in F1, so it doesn't matter).
2. This would mean a lot of maintenance for all the old F2 bots since most have tie defences.
3. This would also cause maintenance of old bots, and it would break the rule against tie feeding in F2. I think this is too drastic a change considering that all bots in F2 are buildt with the knowledge that tie feeding was illegal in F2.
4. About the same rule as #2, but only if your bot creates ties (For instance if it's a multibot). So basicaly if you at any point store a value in .tie then you're not allowed to use .tieloc and .tienum in any way. This would allow the current bots to keep their tie defences, and allow MB's in F2, but still prevent the use of dirty tricks through ties.
Personaly I'm favoring rule 1 and 4... I think that would be enough to keep F2 more interesting and it wouldn't require any changes or rerunning of the league. (Except I think the 2 top F2 bots would need to be refactored, but I believe that's a good thing)