There was a Dedicated Server module for WHMCS... I think I even have a copy of that script, but it's an extremely old copy.
Hmm... maybe I should convert it to Blesta?
I'll look into it and see if there's anything that can be done. Honestly, the closest thing that comes to managing dedicated servers would be NOC-PS's NOC-PS module, but that's mainly for OS reloads and stuff.
Ironically, I have a project right now with ModulesBakery that's currently on hold for developing such a module. It ties into Ubersmith... well, the providers that utilize Ubersmith such as QuadraNet have enabled Ubersmith's APIs.
If you'd like to have access to such a module that makes use of the Ubersmith API for dedicated servers... I'd be happy to get it open-sourced instead of copyrighted and locked to our company only.
Edit: Looks like the module for dedicated servers was abandoned. And a new version of the module has been released for WHMCS.
I'll take a look-see at it and see if I can help with getting it converted over.