It's a no for me, on two levels..Base level, I don't mind a tongue or a fingertip, but I have no desire to be fully penetrated, no matter how enticing people make the sensation seem, no pun intended but the ends don't justify the means.
On the next level, even if I were open to the idea of penetration, I'd probably do it myself. I don't trust a woman physically to be proficient at the mechanics and care needed to safely hump; and psychologically, even if in the moment it turns her on, I think there is an underlying loss of respect at play that will negatively affect the relationship in other ways. I think there's a lot of men that have afterwards settled for sexual acts, and relationship constructs that wouldn't have dared been presented to him if that threshold hadn't been breached, again no pun intended.