This doesn't sound fair.
Issuing more shares without early announcement affects the ability of existing share holders to sell their stake if they want to.
And if we go by Satoshi Dice pass through on bitfunder, we know that bitfunder prices are always more than MPex prices - because of the 30 bitcoin MPex fee. Existing share holders can be screwed any time you see a good arbitrage opportunity. If you want to buy back shares, buy them back from the bitfunder market at the valuations the market decides. You shouldn't have the right to buy back shares from Bitfunder pass through share holders based on the price and valuations on the MPex market.