I think that's a pretty bad idea - the objective is for a team to win, having to tear apart your team every five minutes would be a very complex and niche tactical meta to master and will result in an incredibly slow paced game as lungs tire when teams get down to 7-8 players each. If teams are on even terms after 90 minutes, and cannot break the deadlock after 30 minutes of Extra Time then they're as evenly matched as possible and therefore deserve a way to win that doesn't break them physically. Whether or not they can handle it mentally is another matter [casts an eye towards England...]

I can say that as a player I can stomach a loss on penalties, I wouldn't say that I enjoy taking them but I could handle it. I would absolutely detest the idea of playing Extra Time with my teammates disappearing every few minutes.

Edit: hope it doesn’t sound like I was having a go at you for raising this proposal! On the contrary, I find it interesting when people want to tweak the game in creative ways and talk about it!