The biggest benefit for a true anchor is getting their target allocation, being part of the LPAC, and potentially, getting input on the syndicate.
I don’t think economic discounts should be necessary.
Having said that, LPs like to get a good deal, and hate to get a bad deal. You should definitely give them any MFN type rep they want. Not at all cool if a later LP gets special rights your anchors don’t.
And if you have non-standard terms (e.g., >2%/20%), then allowing the anchors more standard 2/20 terms is an easy give.
But if they need more than this … not sure it’s the type of anchor you really want.