Nice to know you're having good luck with your x10 solution. It's great info for others, who can try to follow your lead.
IMHO - if someone could make a Voxcommando plugin for Insteon and/or Zwave you may find more HA people using voxcommando as there is a need for good VR system for HA but not many around. even HS VR is pretty average and limited.
I know Insteon is HTTP based so I would think it wouldn't be too hard.
I believe at least one VC user is controlling his Insteon devices via Universal Device's ISY99, which has a REST API and can therefore be controlled via the good old scrape action, as per usual.
The unfortunate reality is that to develop plugins, one needs to have the devices in question to do proper testing. HA hardware is expensive, so unless Insteon users with programming skills would like to develop a plugin for VC themselves (which anyone is more than welcome to do), I think it's understandable that James's plugin priorities have been toward supporting relevant technologies that can't
already be controlled by existing, standard VC features in some way -- even if not always in the black box/no effort needed way that many end users would prefer.
The other option might be for a group of users who are looking for custom solutions to work together to pledge a certain monetary amount to cover the cost of the hardware and some of the development time. I suspect that would help to make plugin development for the myriad devices out there much more feasible.