Chansey line, Audino, Alomomola, Togepi line, possibly Chimecho and Ralts line would all work as Love type.
But since all Pokémon can love their Trainers, shouldn't all Pokémon be Love-type?
Love type would be based on the very nature of the Pokemon, I am not referring to natures in the games, as in gentle, caring and passionate. Maternal instincts. All Pokemon exhibit feelings towards their trainer so I doubt this would be what determines whether or not a Pokemon is a love type.
Potatoes have skin and, we have skin. Therefore we are potatoes.
First, we need confirmation that a new type exists. Then, we can speculate all we want about what this new type would be. And among the suggested types, if Love-type moves would be almost exclusively for support, I think it's not worth it.
As cliched as Light sounds, it has a better range for both offensive and support moves. Same with Sound and Fairy.
I´m not really fond about any of those types, anyway.
Love is a crappy type idea. There are no type relations that make any intuitive sense with it. Love is an emotion, not a physical attribute. And people who keep constantly thinking of new types seem to forget why Fairy is the most suggested/rumored in the first place. First you have to think what does love have to do with sylvans? What does love have to do with nymphs? What does love have to do with fairies?