Hey Corey,
I know exactly what you mean, One - 22.5" kettle is not quite enough Real Estate most of the time when cooking for four, I also regularly cook for four.
Like lew and Chris, before me have stated, having more than one grill running at a time is not unusual. like Chris noted, just last week I had rotisserie chicken parts going on my performer, and potatoes and vegies going on My OTG, at the same time. I do have two Weber chimneys, but could have easily done the same thing using just one chimney!, as I started the OTG for the potatoes, ahead of the performer with the chicken...
I too have thought that a 26'r could help when the cook gets a little too crowded on a single 22.5", but a 26'r has not (yet) been in the cards for me! And I have no reservations firing up two or more of my kettles at a time..
I will say however, that 1 year ago, the same day as my first cook on my new 22.5" WSM, I was doing St. Louis Style Spares, I also had 2 kettles running with Larry Wolfe's Sriracha Chicken Wings going on both of them, (and those need lots of tending) I was also making a big pot of Keri's Hog Apple Beans, and my own Cole Slaw recipe. Now with all that going on at the same time, it was a real handful. I will not try that much again without an assistant, I pulled it off though, it was a bit frantic at times. Had that chicken not required so much tending, it would not have been so bad...