I use use some iptables voodoo with them to auto-whitelist on successful auth and blacklist on failed auth attempts.
Three things to note about google authenticator:
1. ssh keys bypass it unless you have a patched version of OpenSSH with multiauth
2. It can be configured to have you append your one time code to your password for interop with things that can't handle keyboard-interactive auth
3. It is self contained and doesn't use any google services to function.
fail2web for me is used on Asterisk servers to watch HTTP auth and SIP. Most of the customers I work with have very strict corporate IT policies, they have to review every piece of hardware and most of the time I can only get an ATA approved. So I drop an ATA on their network with SIP/TLS and ZRTP and they setup the client. However, I don't want to make the assumption that their network is 100% safe, so fail2ban serves me well here.
Also to your point of fail2ban being overloaded, this has never happened to me. I see scans/brute forces all the time add after five fails I usually block the small subnet, and the problem goes away.
All of the solutions you posted are 100% a no go for the problems I am trying to solve.
Using multiple users is great from a compartmentalization / user_management standpoint, but it doesn't protect against brute-force.
I don't necessarily think Fail2Ban needed a GUI, but I guess I never thought it was a "bad" thing?
If I could eliminate any Linux service, it would probably be fail2ban. As an SSH security measure, it's more than useless. If your SSH credentials can be brute forced, that's the problem, and it's easy to fix. Fail2ban just gives somebody a way to lock you out of your own system or to pin a core on your system by overloading it.
If you're trying to add security layers to SSH, here are some suggestions for doing so:
* fwknop (http://www.cipherdyne.org/fwknop/) -- Single Packet Auth based on GPG
* google_authenticator (https://code.google.com/p/google-authenticator/) -- PAM support for TOTP
* knockknock (https://github.com/moxie0/knockknock) -- Single Packet Auth using symmetric encryption