My actual suggestion is to reduce the class limit on Engineers from 3 to 2. I've noticed that there are some (not all) games recently that are starting to feel very Fragmaster-ish with multiple engineers set up in nests or overly defensive positions. Combine this with the use of items such as the wrangler or short circuit, and you are quite literally looking at a formation that cannot be destroyed with even an uber.
If you have a 2 engie limit, it makes it almost impossible to change class to unsap or upgrade teleports at spawn.
If the problem is with the short circuit and the wrangler, then why not blacklist them so they can't be used, rather than reduce the number of engies.
As JJ says, the server is underpopulated even late evening now, and more restrictive class limits will only tend to put off players who might otherwise join.
At times when I play, it is not unknown to have nobody wanting to play engie, and the game just ends up being an endless walking fest for most classes, except for sollies and demos who can jump their way forward quickly.
Having class limits may also deter new players in that class from playing it, as they may feel they are not good enough to support the team. There is a big difference between being 1 noob out of 3 playing a class compared to 1 noob out of 2 playing a particular class.
I would favour removing the class limits completely for a night or two a week (yes, even sniper - I almost feel dirty saying that lol), and see if the occupancy picks up a bit.