I'm an OP on Biffa2001's servers and the last two days he's tasked me with finding something like CoreProtect to run on our modded server. We've used CP for the last couple of years with great success, but he wants to run a 1.10 modpack and without Cauldron, there's no CP. We've only ever needed the logging feature, and that's all we're really looking for now. Well, that and the ability to review the logs for a block in game. There are a number of plugins I've looked at that have this functionality, but they also include interaction restrictions that break mods.
The only other thing that would be handy, but not necessary, would be some form of area claiming without the usual restriction of user interaction in the claimed area. It would be handy to help users space their bases apart. It's pretty common for people to build farms at their bases and keeping them well apart helps reduce issues of inadvertantly loading poorly done redstone or the like. My thought is that the OPs could define a banner (hold a banner with a design and run a command) then provide those banners to the community to claim a radius of 300 blocks centered on the block where the banner is placed. Adding an entering and leaving message would also be handy.
I think it's awesome that the Sponge community is making plugins available within Forge, but I'd like to see more plugins that can run alongside mods without one harming the functionality of the other.