Sorry to necro a bit, but i think its more polite than starting a new topic. I wanted to mention some of the fun that could be had with elves if you think about them a certain way.
Firstly, Cannibalism. If you could have your elves eat their invaders, and create crafts and weapons out of their bones would be interesting. Perhaps a system where you use their carcasses and totems to attract animals to train. Having a greater ability for animal training should be their strength to offset their lack of easy metal weapons.
Magic. Its something that elves out of all of the vanilla races make the most sense to have it, yet probably not of the fireball variety. I'm not sure if it's possible, but having some way to mess with trees would be good, being able to grow tree blocks as we can construct walls would be very interesting. As it would be like shaping trees for them to live in. It would be interesting if there could be a magic that animates wood and plant material items much like a necromancer. Or maybe saplings. Probably not possible though. Some way of limiting opponents from climbing up trees would be a good thing to consider. Also stone tipped arrows and spears should probably exist.
Animal Focused military. Lets face it, crummy wooden weapons aren't going to cut much. Lets have they elves train anything they can for war. I want to see a squad full of war cows beating preparing food beating goblins to death with their hooves. Some method of increasing animal breeding should be something elves can do. Also though its almost definitely not possible, horrific animal hybrids because of elf magic.
I think these kinds of things would make an interesting variation to game play. Half isn't possible, even then the cannibalism itself would make things fun for me.