Wouldn't it be easier to just take a snapshot of all UXTO at the sharedrop date, and users just import their private keys from there - any additional coins created on the research chain aren't included in the new blockchain.
Though the above would be unstable for POS until a sufficient quantity of users had claimed their stake and begun staking..
In your scenario the problem could be solved by initial PoW period.
Which wouldn't be the end of the world to be honest, as long as it wasn't ASIC/GPU mineable and it didn't add serious sync time like the initial scrypt blocks do within the research client (at least that's the common complaint I've heard about the research init blocks).
How are you going to do it? This article is about how to do this bit secure and fair.