I think that it's better to solve difficulty time warp problem in the most obvious and simple way, that is to change the way required work is computed. Currently it is computed as 1/t, that is 15 sec target time is considered to be 4x more difficult (takes 4x more time) to find solution than 60 sec and this is probably not the case. You (and other bot operators) can do some experiments to determine how required time to find solution depends on target time, then we can construct some function that is good approximation of this dependency and use it instead of 1/t.
Another counter-measure is to add checkpoint, it will prevent whole chain forking.
The map shall be enlarged anyway. The current state is ridiculous. Bots or humans they do not play the game but only falling through simple maps. That completely ruined the idea of a mining by play idea. Current state is not stimulating any AI research either.
I think DeepCrypto would agree that any meaningful solution will/must involve calculating difficulty (or difficulties) by some measure of both target time and block acceptance frequency, somehow, and must scale both.
Calculation difficulty shall prevent map preselection cheat. I am not sure that any other difficulty measure would be needed if map will be big enough to force competitors to actually play the game.
And yes. Time warp bug shall be closed somehow anyway. Time warp attack is not very relevant to anti bot measures.