You missed Blesta
We use that and haven't had any issues and it's 99.6% open code, so we can make changes we need. I used to be a WHMCS customer until May 2013, just before localhost.re showed how bad their code was. Whilst I was lucky, a few mates wasn't and had to put their systems offline. But cPanel own 49% of WHMCS so should kick them into place but they would need a full rewrite to do so, with an audit. But people use what they like, Security or Features. Myself I like security.