Not a Pot RoastI see you're serving your guests smoked brisket. Good for you!
If you know much about competition barbecue, you know that many top competitors inject a product called FAB B into their meat. It's advanced chemistry that keeps the meat moist and helps tenderize it too. Hormel uses the phosphate side of the chemistry in their roast beef products. Unless you're willing to walk on the dark side, you're not going to duplicate it. FWIW, you can make your own FAB type inject by dissolving a commercial phosphate in strong stock, adding fat (suet or butter), an enzymatic tenderizer like papin, and a flavor enhancer like MSG. (For what it's worth, I've duplicated these sorts of formulas, but achieved much better results using more natural ingredients.)
In addition to the "better living through chemistry" aspects, I believe Hormel does use steam and pressure cooking, somehow mixing it with a technique called poele, but I'm not sure. The closest you're going to come is using moderate heat and a cloche like vessel like a Romertopf -- which is wildly impractical for your situation.
What would work is good old "low and slow," which you've already got down. I'd suggest trussing your rounds so they hold their shape, and either searing them off or painting the outside with a "browning" agent like Kitchen Bouquet; then roasting in tightly covered pans with a very little stock on the bottom to keep things humid in there. You may even want to try injecting with FAB (or similar), or with a less chemistry driven stock based inject like 3 parts double strength bullion to one part melted margarine. Think of it as larding with liquid. Given the nature of your clientele and of the product, I'd take it to about 190 and allow a long rest. Say 1/2 an hour in an insulated cooler prepped for temp, AT LEAST. Temp is going to be very sensitive -- which is one area where an outfit like Hormel has a huge advantage. A little below 185 and it will be touch as shoe leather; too high over 205 and it will shred. So pull at 190, pack tightly and let the residual heat carry the center to around 195.
In other words, a sort of smoke-free "Texas" barbecue beef duplicating pit conditions in your oven.
In the meantime, make a beef gravy based on the usual mirepoix, roux, the pan juices and a commercial stock base like "Better than Bullion."
I have no problems with Ed's suggestion, which sounds great. Were I a woman, I might even say, "nummy." But it is a straight-ahead pot roast which is something you said you didn't want to do. "Silk purse out of a sows ear" isn't really my kind of cooking except as it applies to barbecue but for one reason and another I've acquired some of these economy short-cuts -- you might as well make use of them.