> One pool having consistently 1BTC more fees to pay out and paying out to these buyers will stand out

hopefully they won't stick out for long because more pools will join the fun too -- every miner loves extra fees!

> They will also know which TX was not in other mempools and its high fee will stand out anyway.

I'm not sure of that. I suspect miners have ways of doing this that analysts can't detect. I doubt chain analysts can see every transaction in every mempool. And there's no reason the fees have to be high. Miners can use normal fee sizes and keep them going for a longer time.