Thanks for the information. In terms of OpenSRS, there is already a community developed module which you can grab here.
In terms of other modules, there are several good developers on the forum here including PauloV, Naja7host, and ModulesBakery (www.modulesbakery.com) that may be able to help.
I was looking into Asterisk integration a bit yesterday, I'd love to have it myself, but I don't think the MG Asterisk integration does provisioning does it?
In terms of HHVM, PHP 7 (Out in Nov) is probably going to end up effectively replacing it. Still, I will say, you may be able to run Blesta on HHVM in the near future.