I'd also be down for an entrance fee, but like TD said, only if everyone else was game.
Honestly, I wouldn't want to change the keeper rules, partly due to my own selfishness.
If I would have known that prices would escalate, I would have kept a number of my "value" players rather than accumulating 3 1st rounders. My strategy would have changed.
The only change I'd maybe like to consider would be making the league a 6x6. Maybe add something like OPS and whatever pitching category you may fancy.