i have said this before, and will likely say it again: moving up should be entirely based on your being comfortable at the new level you'd be playing. if you would be comfortable playing the level above and think you can beat it comfortably, by all means move up as soon as your bankroll can afford losing a few buy-ins there. it also depends on the volatility/variance of games you are playing. for FR hold'em you would need slightly less money than for 6-max, which in turn requires less than if you are playing heads-up or PLO.
peelio had an idea recently, which he has shared here and there as well - how about instead of trying to figure out how many BI you have for the level above, you figure how many you feel comfortable with at your current level. then, add to that a few BI at the level above for taking a shot. thus, say you were playing 5nl so far and are thinking of moving to 10. you feel pretty comfortable and certain that you would not be going broke if you have 30 BI for 5nl (this may be high for some, low for others, so use your own comfort number). so the time to take a 4-BI shot at the next level is when you have 30*5+4*10 = 190 in your bankroll. yes, you will not have too many BI for the next level, but the purpose of a shot is to be more aggressive, to try beating the next level, and if you succeed, getting to the proper BRM levels will be just a matter of time. of course, using that method also requires the discipline to move back down quickly if your shot fails, which has been dumbed a little if you have waited for much longer to move up.
your list mentioned at the end of the OP seems a little too aggro, though. 10BI? there is no level that i would feel comfortable at with this little. even if i am solidly beating something, coolers and downswings happen, and 10BI can be easily lost just like that. if, however, you think that having 10 BI is enough at 2nl and it would be impossible to lose it if you have to move down, by all means do that. just be wary of the dangers (and if you ask me, stick to at least 20 BI - for the level below).