I believe there are authors out there publishing "clean" regency romances, some of them through Christian publishing houses. Julie Klassen is a name that comes to mind, although I haven't actually read any of her books, so I don't know how much sex they do or don't have. In any case, you wouldn't necessarily be treading new ground.
Since I'm not published myself, my advice may be worthless, but I'd say write the story the way you believe it should be written and submit. If an agent or publisher tells you it needs more sex, then you can decide what you want to do about it.
Also, there's always the option of tacking on a wedding night epilogue. You can draw the curtain at whatever point you think is appropriate.
I second this.