Actually, tune2fs applet implements the "-c" option for Max count, but usage show MOUNT_COUNT which is the "-C" parameter So i think it could be a good thing to implement both options (which are similar). Here is the patch for busybox 1.19 master git.
Created attachment 3451 [details] [PATCH] implement tune2fs -C option (current mount count)
The patch is buggy. Fixed it and committed as 46aa5e0859646a1e8f96282b0ab2c362c7565a85. Will be in 1.20.x