I agree that the current system gives some oversight of value. If Mike would like to free up some time, then I think some leagues could establish a committee to make trade approvals in each specific league. Possibly, "founder" owners, if interested, could create a pool for committee work. The committee member should not have a team in the organization he/she is ruling on trades. This could free up Mike. I'd suggest a committee of three, with 2 votes approving a trade. Alternatively, committee of two, and if a tie, then Mike deciding.
I'd be willing to me a committee member in the leagues in which I do not have a team.