I have now 25 k RAC. So this proposal means i need 500k BPP just to be able to continue mining BPP after 1 April?
No, you don't
need 500K BBP to be able to mine (in the case of 20 BBP per RAC), but if you have less, your payout will fall accordingly. So, for example, if you only stake 250K BBP, you'll get about 50% of the payout you'd receive if you would stake 500K BBP.
To be honest, my maximum investment for Biblepay will be 100k. So if I use this for staking, in that case my RAC will be cut off above 5000. Even when I have 25000 RAC with Rosetta, the Biblepay calculation will be according to 5000 RAC. That will be not fair enough for me, so i will consider to quit mining in that case.
However, I hope in the end the proposal for staking per Magnitude will be honored, that looks like a reasonable proposal to me.