My Take on these options
OpenLC Light (no new textures unique to Asia, just a re-allocation / recycling of existing textures for a better landscape
I would rather not compromise on quality so this would be my least favorite choice, unless all the others take too much time.
Mini OpenLCs complementary to OpenLC Light (analogous to regions, e. g. Japan, Thailand)
Sounds too much like the region packs, now if there were a Japan region available, I would buy it today.
Multiple OpenLCs (splitting Asia into a few smaller areas approx. the size of Europe, e. g. Middle East, China)
This is probably most practical since its such a huge area.
OpenLC Asia (monolithic product, practically ruled out - show your support nevertheless)
This would be best but may be too much in one package.