That idea has already been proposed, but it's going to take some time for someone to implement it, the reason that there are quite a few very useful apps already for the N900 is because they've been carried over from the N810.

Untouchab1e, if you only use IM why don't you just switch the phone into GSM mode from the settings? GSM has more than enough speed for you to be able to IM and for it to update widgets in the background.