Seriously I would be all over that, and I would love to see allomancers in space, but it could be very hard to pull off.
(not sure if i did that right)...
Anyway, Ookla...I think the SF allomancers have to be extremely careful, their powers are gravitational, in space it could come off as a 'Force'-like ability and then that's a whole other mess! Now, if they went to other planets...maybe, but can you imagine a Coinshot with bad aim, or a Thug that punches the wrong wall? Or someone trying to Pull/Push...it could get really messy.
I imagine that there could be a not-so-lame way to bring Vin, Elend, and Kelsier back, but not as normal players. I could imagine, that if Sazed can't return their souls, he could use them as spiritual emissaries. The could help share the load of watching over the new world, with occasional whispers and hints here and there. Maybe Sazed could send them to other planets as ambassadors to further his influence on other planets so that in the future trilogy allomancy will work on other worlds. This might work as long as it doesn't go the way of Mt. Olympus and such...
Maybe Hoid is like Sazed, maybe he has the combined forces of one shard that allows him to be at the right place at the right time to further the cause/plight of the story, but he has a 'prime directive'-like rule that he can not expose his power or the answers. Maybe we'll find out that all the stories are indeed on the same planet....Imagine that!!! Dor vs Allomancy/Hermalurgy/Feruchemy vs Chromatic Breathes.....forgive my tangent, but what if one could obtain all 3 powers from each book.... scary individual...maybe Hoid....
Father and Mother....sounds like a RAFO question...