Same problem as always, dragons and dragonkin are extremely powerful and intelligent creatures. You would not find a half-dragon travelling with a group of adventurers.
The closest match is Red Dragon Disciple from the Neverwinter Nights line of games, but this was also an immensely overpowered class due to the sheer number of bonuses and abilities it gains.
I'd like to steer away from demi-dragons/half-dragons/descended dragons entirely due to the nature of incorporating them into a game like I'm planning. They won't be fun for you to play because any "iconic" dragon abilities will fail in ANY dungeon environment. Shapeshift to a whelpling and your main attacks are dragon's breaths. I don't think anyone in melee range of an opponent would appreciate having to make numerous dodge rolls to avoid the opponent's abilities AND yours dragon breath abilities. Anything bigger than a whelp and you'll encounter size issues in labyrinthian tunnels meaning you'll be spending all your underground time in your humanoid form with the exception of major boss battles which will usually take place in cavernous areas where all abilities can be used that rely on large amounts of space.
It's not really in the spirit of the game to have the other 4 drag a relatively weak character through the "mundane" parts of dungeons and labyrinths (although most battles will be fairly well tuned) then have the epic boss battles spoiled by someone who's flying around searing everything with dragon breaths, resisting all magic attacks etc.
Trying to come to an effective compromise is - as always - difficult. Balancing your race choice with a set of basic starting abilities that will allow you and your group to act as a team, learn together and develop together as you make your way through my planned game world is extremely tough when you pick what would normally be predominantly NPC races or classes. Lycans, dragonkin and similar races have to have their power toned down immensely.
By standard convention a every time a Lycan feels pain they have to make a Will roll or transform. They then need to make an additional will roll or become feral until dawn. A race like that would work against teamwork and wouldn't be fun if you randomly lost control of your character every time you were attacked. So I slap on a massive negative modifier for your communications.
Shopkeepers and innkeepers would charge your group higher prices for being associated with a lycan (in order to discourage the adventuring group from staying around town too long). Villagers and townsfolk would be far, far more reluctant to assist the group and may lock themselves up in their houses for fear of a lycan.
That's why I wanted to take control of character generation. Looking in other RTDs you've got Enchanted Motorcycle Tickle-Mimics and Talking Pony Voodoo Princesses. You can't really forge a respectable story if the characters and classes within them aren't reasonably balanced or who don't hint of teamwork and that's what I am aiming on doing. This is going to be a long-term adventure afterall, there's plenty of room for individual development.