This is impossible.
Question, who paid the 3% a year?
The answer is nobody, it like something fall the sky, or a perpetual motion machine.
It seems like you dont understand what POS means , and it is not about someone paying you for the 3 % or anything. perhaps you want to read about POS coins again
People can't even agree to a simple fork to increase the blocksize to 20MB. Why would you think that forking Bitcoin to a Piece-of-Shit coin could stand any chance of happening?
This, we can't even get the community on board with a no brainer. If you think that you could get it passed go for it, the code is open source, make it work and try to get it to go. You might even get a few people who will jump over to BTC-POS but it would just be another alt coin.
Changing BTC to POS wont make it to be altcoin but I do agree that it will be a very useless thing to do .
Changing to PoS could solve some problems, like the problem of current miners crying for more fiat as income.
changing to POS wont help anyone because if BTC is change into POS then the value of it will drop too, leaving it meaningless to be just useless coins and not BTC anymore. Forking it in 20mb block will atleast make some decent effect to that