Specifically regarding Skirk Prospector, but applicable to all cards like him. His ability states: Sacrifice a Goblin: Add {R}. Rather than having to activate his ability individually for each {R} I want to add, when I activate the ability, allow me the option to, like X spells, input the variable, thereafter being allowed to select each of the creatures I wish to sacrifice. I played a game the other day where I needed to use a bunch of mana to be able to pay for an attack due to my opponent's use of Ghostly Prison but the only way I could do so effectively was through Skirk Prospector, but even though I was being completely active throughout my turn, the timer started going down and I couldn't move fast enough to do what I needed to do which, inevitably, cost me the game. And yet there's this one asinine card that whenever a +1/+1 counter is put on a specific creature, it's controller creates a token. Combine that with an effect that whenever a creature enters the battlefield under that player's control, put a +1/+1 counter on target creature, and this guy has a literal infinite loop where he's just creating creatures out the wazoo and there's nothing I can do about it. But even though this effect causes the turn to be taken up ad nauseam, he doesn't get that timer. Making it so I can select the amount of mana I want to add through sacrifice by activating the ability once would drastically speed things up.