Have you looked at the Leviton hard wired solution?  I think it's called Lonworks?  It would
very likely have decora switches.

The X10 protocol is not very nice for a large installation -- it is slow and subject to a lot
of problems with noise.   I'm using 3 or 4 housecodes.  I've tried Active Home and the CM11a
and moved to the AD Ocelot. It's a great system for someone who likes to hack at home
but you have to be careful about resale and not do anything that can't easily be unplugged.

If you can afford JDS Stargate you should look at a real commercial grade hard wired system.
I'd be interested in knowing what you would be quoted to do a whole house addressable system
as X-10 and as hard wired.  My X-10 switches, whole house surge surpressor etc cost an additional
5-6K.

MH is a great system for perl hackers.  I'm always amazed at the level of support people get
for problems from everyone on this list and especially Bruce.