I think that if the stake rate is increased in a way that is consistent with the goals of Magi it could actually help reduce the current inflation from over PoW mining. This could be done by improving PoS-II into PoS-III, which should reward smaller holders the most. The stake rate should go up the most on small blocks. I think 10% for any block under 100 XMG wouldn't be too generous, while 100-500 XMG could stake at 7.5%, 500-2500 at 5%, and any block over 2500 at 2.5%. I get a lot of stakes from small blocks, and the reward is often 0.02 XMG for anything small, and around 0.15 XMG for a 2000 XMG block. This is much less than any PoW block, and could be safely increased without causing inflation. Being able to set the split threshold would also make staking much easier.
If we want Magi to stay a CPU only coin, changes to the algorithm should be made, if only as a preventative measure. Even if the miner that turns on 48 MH/s isn't using GPUs, that doesn't mean that one couldn't be developed in the future. If it can be done, it will if the profit motivation is there. I would prefer that changes were made to the existing algorithm to make it more GPU resistant, instead of basing it off of something completely different. Maybe M7M2? This should only be done after there is an optimized CPU miner that is ready to go so people only have to download an update to the Sweetspot miner, which would be easy for the common user.
The PoS-II approach was designed with similar feature, though not direct inverse rewarding route. I am sure I'll take a closer look systematically. A simple procedure for a big holder to take the advantages is to split his coins into small pieces, and as to each piece he'll gain equal shares as small holders. An optional approach is given "rules" and "efforts" are made barriers to the big holders and mitigate advantages gained by them in a way unusually. This is not straightforward, though PoS-II is supposed. You're right, everything needs to be ready before going, mostly launching testnet for the test.