What I *think* you don't understand is that those of us that are already mining don't get anything from your proposal. Since I am already mining, what do I get for lending you $100? All I get is $100 less in the bank. This is because I am already mining. Lending the $100 does not add to my hashrate. The borrower doesn't even have to pay anything back.
The borrower still has to repay the loan. .the mining is just a bit of incentive on top of that.
Let me try to put it another way... when you are mining, what guarentees that you'll earn some coin? Is it just dumb luck? or is it something else? Are others trying to earn those same coins, and can they undercut you? That is what I am trying to take out of the equation. You get to procees a block that nobody else can.
If you are already mining to your maximum capacity then you can sell your rights to THIS BLOCK to someone who is able to use it.