That's not how this works...that's not how any of this works....
Your solution would increase the gil in circulation, I do not know how else I can get that across to you. If you dramatically increase the gil in circulation the gil itself becomes abundant, with little to no gil sinks to REMOVE the gil from the server at a steady rate, it increases rapidly and it starts to have less buying power. With less buying power the prices on the market board will increase, but not in the way you want them too, they will increase relative to the influx of gil. This will not solve the issue you are having in the first place.
Your next suggestion was to cap prices on the MB to counter this effect, again, completely destroying any type of Free Market.
Then you stated a free market had to have everyone on equal footing which is when I just /bow out of the thread as that's just a ridiculous statement as a free market does not care if you are rich or poor, only on the supply and demand of an item and what the market deems its value to be.
I really have no problems with people trying to figure out ways to solve economy and RMT problems and I would be behind you 100% if I thought this was a good idea, but it isn't.