If it is large enough, why not move the laser instead?
In an SLM machine you have a cavity that is filled with a fine metal powder, the laser selectively melts/sinters parts of that, the base of the cavity moves down slightly and more powder is added to the top. Rinse and repeat until you have a solid part in the cavity surrounded by the powder that wasn't touched by the laser. I'm not going to cop-out and give a link to wikipedia, but if you go there and only look at the block diagram you'll see why the bed needs to be moved with precision at least equal to the minimum feature size that you're aiming for.
What this project aims to achieve is akin to 3D printed plastics where the raw material is deposited right where it needs to be instead of selectively converting parts of a much larger amount of feedstock. I suppose you could move the laser if you want, but it on the face of it I think it would be simpler to just use a few mirrors attached to servos to direct the beam where it needs to go.