Make it a 3 game series for sure. Give all the other teams a break for 4 days. Make them play back to back nights. Day off for travel. And the clincher if needed day 4. We already have had this "wild card" round once every few years. It's called a tiebreaker, and the giants and somebody else did it a few years ago I believe.
Nice idea, to bad the idea is only half baked right now.
Here's my plan-
2 leagues, 2 divisions per league (either a 15/15 split with continuous interleague play or a 16-14 split)
12 teams make the playoffs- this is still a smaller percentage than all other major sports.
In the first round, the 4 divisional winners get byes and the 8 Wild Cards play a best of 3 in the park of the better team. Season ends on Sunday and all the Wild Card series start on Tuesday ending on Thursday. Divisional playoffs start on Saturday so the 4 divisional winners have had only 5 days off. Divisionals are best of 5 and Championship Series and the WS are best of 7.
This format gives the division winners a major advantage over the WC winners making the playoff races more important. The division winners will be able to set up their starting rotations and the bullpen will be completely rested. WC teams will want to have home field advantage making many more games in September important. And just think how great the Wild Card week would be? 4 games on Tuesday and Wednesday with deciding games on Thursday. You want excitement- here it is!