mac.calder

Most LCD TVs will have onboard scaling - so they will support a range of resolutions up-to and including 1080p - if the panel is <1080p is will downscale. You don't need a presetation switcher, all you need is a scaler to help interface with an unknown "random" device. This from Kramer for example. Run your stuff at the highest resolution you can afford - so HDMI 1080p if you can afford to and then have a scaler available if the onsite projector is not HDMI compatible. Downside is someone needs to know how to set it up... the upside is they are not that complicated.

The grandMA will not output DMX without an MA output node or processor on the network. You can use MA-3D because they communicate in MA-NET speak. I don't think there are built in allowances for other visualisers.

Another method (a tad messy if you want mobility) - the larger clearcom user stations (ie the 4 channel matrix systems) have a Program input - you then assign the program feed to a channel, then when you listen to that channel, it mixes in program audio. Overall balance is controlled by a knob on the front pannel. If mobility is really an issue, the propper 4 pin extension cables are not THAT expensive (just make sure you get the right stuff... scroller cable will induce a heck of a lot of noise).