As i said, UEFA will just block it. Cardiff and Swansea are allowed as the Welsh League is amateur, but if the league is professional they won't allow it.
I've always thought the play offs were a bit unfair, as they offered no reward to the teams finishing higher, sometimes 5-6 wins ahead of their opponents. I'd follow similar to the Super League system in rugby, all ties over 1 leg:
Match 1 - 6th place away at 5th
Match 2 - winner match 1 away...
It's amazing to look back at just how run down Stamford Bridge was prior to it's rebuild. The away end was shocking, and the views were terrible as you were a mile from the pitch.
That article is from December, but it's still being looked into, this article was in the Guardian last weekend:
http://www.theguardian.com/football/2016/apr/11/leicester-city-finances-football-league-financial-fair-play-investigation