Although mining Protoshares with the hardware at home doesn't make a lot of shares any more, some people (like donschoe, or me) still do it because they believe in future profits. The electricity is paid anyways, and (at least in here germany) there's a final bill at the end of the year. I don't believe many of those miners would take 30$ a month and buy btc to get more pts.
There are others who don't pay for electricity because they have a "all-inclusive" contract (at university residential for example).
So it really would leave the small guy behind.
I don't think you'd break the social contract, at least not in the beginning. If I had 1k pts now, I knew I would have 0.005% of every upcoming dac. With the new idea I get more for dacs developed in the next 4 years. After that, I get less.
Maybe the solution really is somewhere in having two assets. PTS decentralized as they were intended. AngelShares as Invictus fundraising but limited to 21 Millions, with a decreasing output every week.
In that way, no one can blame you for not honoring the social contract, because pts holders get at least 10% of every new dac.
Little guy can still mine pts for a while.
Invictus gets funds over a planned period of time, after which it should be able to work without that.
Value of pts isn't inflated.