More so, it's ironic, that you should call your coin GPUCoin, when you're leaving the door open for an ASIC to come in an limit the GPU's effectiveness.

If your intent is to create a GPU based coin, that is then able to be used to purchase additional GPU's, then I'm in as well!  But given that coins like Ultra/Vert etc are already heading down this path, the only key point of difference here is your linked in shop that only accepts GPUCoin.  Assuming that GPUCoin will end up on multiple trading platforms, the need to directly mine this then becomes less of an issue, if it can just be bought.

So, if you're intent is to create "GPUCoin", then ensure that you're putting your best foot forward to ensure that this is ONLY minable with a GPU (for the foreseeable future).