Well, he always has the option of asking the facilities to match the addresses to his requirements. This shouldn't be anything out of the ordinary.
In my opinion, based on darn near every theater I've worked in, dimmer packs were in a rack or racks, easily accessible and channels could be changed very quickly. In the "other" theaters that couldn't do this, they didn't have anything outside of house lighting because they were not positioning themselves as a facility that could handle theatrical performances(despite having a full stage, backstage, production booths and dressing rooms, go figure).
Typically, theaters are going to centralize the lighting control into a rack or racks for ease of management and control purposes. From there, they'll run long power cabling. I'm not sure what they are running but I've seen both Edison and Stage Pin configurations used.
This leaves the oustanding issues of gel sheets. I've always seen this being a problem. The solutions have ranged from house guys grabbing ladders and lifts to change the gels ASAP all the way to "go f*@! yerself" and everything in between. You can tell the better theaters, they are more accomodating folks.
With that being said, MyDMX can work just fine but it would be recommended to get the Elation DMX-Branch/4 for added protection, signal boosting and splitting as necessary.
My opinion: Working with lighting companies that can handle touring acts(but aren't touring with the acts themselves), I've found them to be prepared and willing to reconfigure almst anything and everything to accomodate the client. This tends to not be a big deal because most have specified gels and configuration stuff in advance, so the lighting company is prepared before they arrive on site(or at least before the par can trusses get raised on motors). With theaters, I only find issues with gel sheets and rarely do I have issues with the techs. The biggest issue tends to be racks of dimmers not properly labelled, and I don't see that too often.
Sounds like he could go either way(MyDMX or CompuLive) with more than acceptable results, provided the techs at the facility are willing to cooperate. That's a BIG "IF".