The best conflict would be a hero with a deep dark secret that disturbs his ability to have a good relationship eg being a vampire, a sadomasochist, etc etc. You might wish to extend the repertoire - supernatural beings seem to be popular at the moment. Try a zombie, werewolf, or, if you prefer realism, a Scientologist. I do not approve of Scientology however. If he was a member of a cult orgy that have flings in a tub filled with ice-cream it might be unusual, but kinky and disturbed I doubt. There's something in black leather corsets and sharp fangs that appeal to our Gothic sensibilities. If you are still attempting a Regency romance I suggest a Highwayman hero. It did work for Edward Bulwer-Lytton's Paul Clifford, a bestseller in the 1830's. Whatever your hero is, he is distant, aloof and morose - unattainable by most people, and only the heroine can reform him. No one can ever understand him.
I suggest a hero who enjoys cross-dressing and wandering round the streets in women's clothing. He keeps female lingerie in scarlet shades and a great deal of corsets. He fears it will affect his ability to have a relationship as he secretly enjoys being dominated. Dominating men being in fashion however must put an end to this. We could have a crazed Nazi wannabe who likes women dressed up as Gestapo officers, though this might be too controversial. N.B. Check out Allo Allo for a comedy treatment!
My example would go along these lines:
Christopher Blue was a plushophile, that is to say, a person with an unusual fondness for having intercourse with teddy bears. It had all started when a school bully had shoved a teddy bear down his trousers, and he had been excited by soft toys since. He would go to toy stores ostensibly to buy something for his nieces and nephews but in reality to indulge in his most perverse desires. He had had several partners over the years - an elephant, a giraffe, a hippo, a rhino and several pandas. But his constant partner was a teddy bear called Antonio. Women had failed to excite him as much as his animal friends, and he consequently avoided their overtures unless they had the grace to dress up in a teddy bear costume ... "Aphrodisia," he said, with longing passion in his eyes, "will you agree to have an ice-cream orgy with me and Antonio? It will be so much fun. We will roll around in gallons of raspberry ripple, licking the tub with our passion." Holy crackers! What could I do? The idea of having it off with a stuffed toy held no attractions for me, and I shuddered to think he preferred the bear's favours to mine. I began to shiver as he described enthusiastically the various positions he had indulged, and how I might please Antonio, who it seemed was a pretty kinky bear. He had bought a bear costume for me, but he would do nothing till I had signed the contract to be his Bear. Oh, holy lasagne! Could I but bring myself to Common Bestiality? I had loved my own bear to bits but the thought of letting Christopher sink his unbridled lust into my Cuddles was beyond imagination.