Ok before I sound like a complete a**hole. I should mention a compromise, say 50% ownership until "your" miner arrives.  After that then you're 100% vested.  So here are the scenarios:

• 1. Everyone's 100% vested from the begining
• 2. Once the nth miner is received only shared that helped buy all miner up to that one are 100% vested
• 3. Once the nth miner is received shared not represented by the remaining miners are only 50% vested