Do I accept the offer and risk opening my account to changes that may result like lower QS, and possibly end up getting banned somehow when they realize I am a lowly affilate?
We did have *one* campaign where they did improve the return and we kept their changes.
If you want to try them out, let them do *one* campaign, and have it be a new one, not one of your existing ones (or at least save/pause your existing one so you can go back if you need to)
Do I accept the offer and risk opening my account to changes that may result like lower QS, and possibly end up getting banned somehow when they realize I am a lowly affilate?
When you get your account optimized, you get a proposal - meaning - you see all the proposed changes and have a chance to accept/decline on campaign/ad group/whatever level. No a single change is applied without your approval, and everything happens within the interface. You won't talk to anyone.
So, from that perspective, you can only learn by browsing through proposed changes, being that how good their optimization is, or bad.
Anyhow, even if you don't like it, you may still get a clue about stuff you never thought about before.
For the second part, it's really up to you to figure how this could affect you down the road.
There is nothing concrete, but a guess only.
I personally think that the group (or individual) that would work on your account have no connection to automated or manual reviews, nor they're in any direct connection to the policy team.
Furthermore, being an affiliate should not entitle you into "banned" group, but I totally understand you fear which is based on the posts like here at WW.