Why not? if you guys manage to hit a block you can check his hashrate/shares and then pay him accordingly, all you have to do is get him to mine to the same wallet using a different worker, actually his idea sounds interesting to me, whoever doesn't have BTC in hand can contribute some hashrate, it will be a bit more difficult to manage once and if a block is hit, but as long as everything is planned for ahead of time then there should be no problems.