trohat: Imagine you play e.g. 5-win match and because of bad time management (reason can be some family business or easily some unexpected party with friends) you lose one of those games on timeout. Would you like to lose the entire match ??

Well, yes, I would like that to happen. You'd lose the match if it's a 1-game match anyway - family business or unexpected parties or not. I don't see why a multi-game match should be an exception. Heck, I can argue that in BK, it would even make more sense: considering that for ratings, win/loss ratio and tournaments a 1-game match has the same weight as a 21-point cube match or a 5-win match, BK treats a multi-game match to be a single game, so it kind of make sense to do that for timing as well.

trohat: To make my argument stronger, imagine that this game is with a very weak opponent and the loss would ruin your BKR

It wouldn't ruin it any more than losing a single game match on timeout, so I don't see why it would be 'too hard'.