Lol, i live close to the Dome and had this exact idea last year, but ran #'s and seemed like it was way more trouble than it was worth. Thought I could bring in $100 / day at very most, which hey I guess is not bad money for 2 hrs of my time, but i just let it go.
Also I'm like 95% sure that I've purchased tix off StubHub, and run my phone under the ticket scanner at the gate and it worked fine, just as if I'd run a printed sheet under. And the stadium staff seemed fine with me doing that, so not sure why they say you MUST have printed tix...
(don't quote me on the above; i could be mis-remembering, but i really don't think so)