... the AEON approach of allowing limited use of 0 mix and non-RingCT transactions would allow things like pool payouts where both tracing and hiding amounts is largely pointless (the blocks mined by the pool is generally public anyway, as are the payout transactions) to be done with lower cost. Or at least, they would bid for access to the quota of 0-mix transactions. My guess is that those slots would be most valuable to pools for cheap payouts, but I don't know. The market will sort it out.

I don't see RingCT or required mixing being a problem here at all. People who don't need it can opt out, as long as is kept under control and doesn't compromise the privacy of the chain as a whole...