I don't know about the lilac as of yet - I got a 2' dwarf Korean one like a month ago, it was pot bound, so i put it into a slightly larger pot - root pruning will have to wait until either fall or spring - i have yet to find out which will be better...
I am a beginner at bonsai, so that alone might prove fatal for the tree, but as i understand it, the basic techniques should be able to keep it alive - the main points are properly draining soil, and maintenance of the roots - whether you style the top or not, doesn't much change its living environment...
It bloomed quite well and lasted as long as similar ones in the neighborhood. I took cuttings and pruned it back quite heavily, just as it was done flowering (timing for that was suggested to ensure it flowering the next season - which would make DH happy), hoping that, if i kill it, i will have some cuttings to work with.
Whether it will survive will largely depend on the root pruning and how it is overwintered (it's supposed to be good for zone 3, but that's in the ground obviously).
Bug me in spring and I'll let you know how it's doing
If you're moving anyways, i don't see much harm in trying to take a few suckers along, even if the whole plant is too big for a container... The variety shouldnt matter too much, i got the dwarf variety because it has smaller leaves (considering the planned bonsai look)
Just separate the sucker from the mother plant by driving a spade inbetween them, and let it grow for a bit before removing it. - Depending on where you are they grow like weeds and you will have hard time killing them no matter what you do :p