Is there are market? Like every other conceivable niche the answer is yes. How big? Who knows. Worth the trouble? Who knows.
Afterall wasn't the orgin of the term "professional escort" someone that is compensated to accompany another to events where having a date is socially expected?
My biggest concern or piece of advice would be to figure out how avoid misunderstanding about what is on the menu. Afterall just about every ad ends with some kind of disclaimer about how the fee is for time and companionship only...wink, wink...
I suspect your clientele would skew much older. Are you comfortable with that?
And as far as the discount for future (full) services...selectively offer it as a courtesy if you want but I'd caution against it as an integral part of the offering. Keep the "balance sheet" clean. at the end of the date neither party has any obligation to the other (including some future discount).