I didn't know that obtaining vices was tied to the movement of the respective units in MTW too. for sure it's the case with RTW, but this is an interesting insight

since MTW tends to have so many different faces (just check the barques vs. caravels thread: https://forums.totalwar.org/vb/showthread.php?t=78202) I can only speak for what I found to be unseful. for example, a good way to avoid vices on governors is to keep taxes on "high" (i.e. lower than very high) most of the times. also, the kind and frequency of vices seems to be affected by your general standing. if you are the mightiest faction or otherwise exceedingly rich your governors will soon start getting those "exclusive trader"-like vices. they're not nice, especially as they decrease further (in my games most of them disappear on reload, though....).

in general the best way I found to avoid vices is to let those guys fight often, preferably as the general. this is not always viable with governors but keeps them peppered. and finally .....build new units to maintain a constant flow of new, potentially capable governors since in my expreience the old ones *will* start detoriating one day. not necessarily and not all of them, but it's never wrong to shuffle the gentry around which gets lazy from sitting on its a**