And how's that going
https://stats.cubecraft.net ; as you can see, 1.9 always has many, many more people than on 1.8. If not the hackers and if the anti cheat actually worked more properly in 1.8, I think 1.8 would indeed have a massive potential in Cube's player count; but that's much easier said than done and I believe focusing on the 1.9 community is better than investing too much in a probability. All in all, I think the current 1.8 games that are available are fine, I mean, do you really want to play 1.8 parkour? How's that gonna be any different, same with tower defense. Might affect it in Minerware indeed, but most people playing it aren't that skilled anyway.
What games do you want to be in 1.8? I don't see a point exporting any other game mode than the ones that currently exist.