I wouldn’t endorse a strict tit-for-tat arrangement. All else being equal I don’t think I’d ask a partner to do something I would be utterly unwilling to do (or do the nearest equivalent of, if any; some things really don’t have a close reciprocal equivalent, especially in couples with different genitalia), but if she wants to do X and I want to do X and neither of us is really interested in counter-X, that’s fine. Just because some aspect of a relationship is objectively asymmetrical doesn’t mean the participants experience it that way.
I certainly don’t think anyone should say “I have no interest in doing counter-X, regardless of how you feel about it, therefore there is no fair way to ask to do X”
And yet, while this is true, men and women are also extremely similar in all these ways. It really isn’t that hard to generalize physical sensations across sex boundaries. The genitals are very different…yet surprisingly isomorphic.
In any case, individuals are very different, and so the only way to make sure you’re maximizing the pleasure of the one person you’re with is to ask. Communication is the key to good lovin’.
Some people want hard, fast, rough, pile-driver sex…and others want slow, gentle, soft, soothing sex. Experimenting with an outside partner won’t help you learn what your real partner wants.