>>11318582
Hmm... I haven't really thought about any of that.
i don't really want grail war or life and death situation. Maybe two master can wager their servant, so winner takes loser's servant. If a master loses all of their servants, then they can do a last resort and become a servant temporary to win back their servant, but of course, if they lose they will be forced to become the winner's new servant. Masters could maybe trade or reroll servants they already got the same one already. So if the winner already got Ushiwakamaru rider version and the loser master was turned into Ushiwakamaru rider version then they can be rerolled or maybe altered to other know version like Ushiwakamaru summer which is assassin class. People won't be completly rewritten personality wise, but will pick up personality traits servant would have like Ushiwakamaru's desire of getting praised and headpatted, Tamamo caster saying mikon etc.
Maybe fate/go's bond system could be used too, where if you fight together often then master and servant will end up liking each other more. Depending how compatible the two of them are the bond leveling could be faster or slower and could level up from just enjoying each other's company.