How are you planning to hedge against a heavy fall in the BTC/EUR rate?  I'm not aware of any cheap high-volume means to do so (other than converting into fiat which would be rather pointless).

Your plan pretty much relies on BTC rising vs EUR.  Whilst I'd tend to agree that long-term that seems likely it's also likely that any such rise won't be a steady one but will have the occasional large bubble + collapse.

If BTC happens to be at the top of a bubble when you launch it could be rather a problem for you.  Whilst you may hope your own purchases could extend the bubble you can't really base a whole business plan on hoping BTC doesn't have a collapse shortly after you start taking deposits (if it happens later then it isn't such a big problem - after a while only a total collapse of BTC would be a major issue for you).

It's certainly an interesting business model - borrow money denominated in EUR then bet it all on BTC rising.  And rather than paying interest for the loans to speculate with, charge them fees for the privilege.