I haven’t used raidz but a quick search tells me it supports single-drive expansion.

Maybe reconfigure your raidz as a 2-drive system, then copy over all your data into it, and expand it back into a 3-drive system after.

Well I figure he does want control.

Also, if theres two competitors and both could give more than a 2x return, then its a safe bet. The only way its an unsafe bet is if they can both fail, but hes clearly not thinking about that kind of thing.