You're missing my point. Whatever you set your auto-lend to, others will react to the presence of your swap offer and undercut you if they so choose. That's just the nature of the beast... it's a market, people want their offers filled, so undercutting happens all the time. You set your rate to be "FRR minus 0.1", some other guy will set his to be "FRR minus 0.1001" and a fixed rate offer will pop up just below that. The only way you're going to be able to avoid being undercut by other offers is by taking an active hand in placing your offers, or running a bot to do so for you.
Source: I am undercutting you constantly by manually placing fixed-rate offers.
You are assuming that every lender is willing to accept the same interest rate, which is false. I may be willing to undercut more than others to get my offer filled. Or less, and see my offer waiting (like it happens now with FRR).