In the file rebellion.user.setting, there is a line:
LaggingPlayersToleranceForDropping 500
I am not a modder; I don't even play one on TV. However, this could be the line you would want to change (my guess is that you would want to reduce the number to get the AI to hang on longer, but you would have to experiment to find out). You can probably edit this file in Notepad and then change the extension after you have saved it initially as a .txt file. As always, save a copy of the original file somewhere so you can restore it if things don't work out.
Many of the lines in this file appear to be set automatically based on preference selections, although I agree with selereth that I have never seen an option to change this when starting a game. So it may re-set automatically (with some defaults pre-set in the game engine itself) at the beginning of every game, in which case the time to edit might be after you have started your game, not before. If that doesn't crash the game in and of itself, you should be good to go, although you might want to re-check the file after your first post-edit session to see if it has been overwritten.
Anyway, if you want to experiment, best of luck. If you do, reply again on this thread and let us know what happened. Thanks!