To reiterate what ZeroVega said regarding reiterating what I said...
I would advise against making any assumptions as to what can and cannot be done regarding subrace skins, custom appearances, and so forth until we have the game in-hand and have had a chance to work with it a bit.
I don't want to dash your hopes of this half-giant character, and so I would suggest not going too far down the road of development and backstory until we can say for sure what will and will not be possible.
I'm sorry, but this is the best answer I, or anyone else on the Development or GM teams can give at this point. The fact is we don't know, and it's entirely possible that half-giants will not be possible in the initial release of NWN2 and/or the next version of Layonara. We do not have game code, we have not had any time to work with it and experiment with subraces. Besides what has been announced and confirmed officially by Obsidian, there is really nothing we can say with any semblance of accuracy regarding NWN2. At this time, anything not officially confirmed is speculation, and it would likely be a bad idea to become too attached to an idea rooted in speculation.
I really wish I had more definite information to provide, but I do not. You really need to consider the fact that you may be disappointed that half-giant characters will not be available in NWN2.