If only i had the private key i would maybe pay like 101 BTC for 100 BTC mined to my address.
So yes there could be a market
You only need the address for mining not the private key. The problem is that most mining pools do not disperse shares directly from the generation (coinbase) transaction, so for most pools you would get some mix of non-virgin coins. As mentioned above Eligius and P2pool both directly split the coinbase into shares paid. The downside is this takes 120 confirmations before they can be spent (unless that was changed, I haven't really followed it). In any case whether you or someone else mines the coins go to an address provided.
If you wanted to provide a service providing virgin coins then you would accept a customer's address and mine to that address for them. If you wanted to pre-mine such that they can just buy them (without waiting) then they have to trust you as any split key method would requires they provide a public key such that you generate a shared private key that is trustworthy. In which case why not just mine to their address.