Talked with Chris (Tenpoint5) and we compared notes. I took a very different approach. Mine is based upon the label ingredients and what I suspect is being used (grill flavor) based upon what little I know about some food service products. Here is my feeble chemist's attempt to produce a clone. It is very feeble as I don't have a reference by which to judge. What I plan to do is send it to 10.5 and let his tasting panel evaluate this first trial.
The big challenge is to get grill flavor. The very basic versions of that stuff are made by pyrolizing vegetable oil. Since that isn't practical in the home (think controlled grease fire) I had to get creative. A common tool use in the spice blending trade is to add a vegetable oil to blends at the 1% level to prevent separation. So I thought I could use that idea to coat a veg oil onto the salt, burn it in the oven and then use that salt to make a clone.
The drill is as follows - 250 g of Morton Kosher salt + 7.5 g (about 3 tsp) of Wesson Best Blend (canola + soybean) oil, blend it in a KA mixer on speed 2 for 3 minutes. At that level, 3% oil) it is surface saturated as seen by traces of oil remaining on the bowl.
The coated salt was then placed in a saute pan and oven roasted at 500 - 550 °F in a convection oven for 3 hours. That gave this as the salt.

A few pulses through a blade grinder and it looked like this

Flavor of the "roasted" salt is very mild grilled flavor.
Now to blending. I like to target 2% salt to meat by weight. For MSG I looked at Accent's recommendations, which amounts to 0.4% (MSG) to meat by weight. That gave me a ratio of 20% MSG to salt. The rest is looking at relative amounts to salt of flavor spices in other blends, like Montreal Steak Seasoning. After all the head work, this is the blend mix I concocted:
Treated salt = 100 g
MSG (Accent) = 20 g
Granulated onion (Leggs) = 15 g
Granulated garlic (Leggs) = 10 g
Black Pepper , ground) = 8 g
Jalapeno powder = 6 g (Thanks CRG! - didn't know it, but I was out)
Veg oil = 1.5 g (~ 1/2 tsp)
Put all the dry in a KA mixer with the paddle, speed 2 for about a minute, add the veg oil and continue on speed 2 for about 3 minutes. Here is what you get

I would describe the taste as meaty/salty/lightly grilled. I would like to have a more pronounced grill flavor. Doing that the way I did would probably take a second trip of treating the salt and back through the oven, which is more than I am willing to give it at this point.
If Chris is up for it, I'll send it to him and let his professional taste panel give it a whirl.