I definitely think CubeCraft should add 1.8 versions of those games you mentioned. I used to play SG when CubeCraft was 1.8 and in my opinion out of every server it had the best SG there was (maybe minus MCSG, MCSG was the best for SG no doubt(its not a server anymore >:v I'm allowed to say that)) I really feel though if they did add 1.8 SG they should go for more of a classic feel rather than how SG is in 1.9 with the world events and the items.
What I'm going to say is partially my opinion and partially fact, I dont want to annoy anyone or argue anything. What I'm going to say is this, not having 1.8 gamemodes on the server is cutting a whole section of the Minecraft community out and CubeCraft is missing out of so much potential growth by not having many 1.8 gamemodes. I have so many friends who left CubeCraft because they didn't like 1.9 pvp and don't want to play on here because there isn't a 1.8 version of the game they like.
Also I would like to add to respond to people who think "all they have to do is try 1.9 pvp and they will come around and might eventually prefer it". This simply wont happen, players dont want to leave behind a version they enjoy playing and that's fact. They wont leave behind what they enjoy to something they don't because they "might eventually like it". Yes, Minecraft will continue to develop and maybe one day we will be seeing the version 1.22.3 but it still doesn't matter, as long as there are players playing 1.8 and as long as that community its still going they should be welcomed. Growing isn't about what they players we already have want, yes the updates that are brought to the server should make those players want to stay but growing is about reaching out to the players who aren't on the server and giving them a reason to come on.
I think asking this community as it is now wether 1.8 versions should be added will get you a very biased answer, obviously not many people will be too bothered about it because most of the people who are already here are her for the 1.9 versions.
Ok... Lecture over :D