Best bike I ever owned (and put together) was a Powerlite Cruiser with Araya rims, Bullseye hubs, stainless steel spokes, Specialized knobbies back in the '80s, alloy cranks, neck & seat post, BMX bars, Haro 2-finger levers, Specialized grips, etc, etc.
What I call an "adult BMX bike!" You could lift it with a finger, it was that light... and I put it together to ride parks & pools back in the day. A real performer in the vertical world, and then it got stolen... grrrrrrrr.
I hope the wanker who stole it got hit by a truck... his bad karma catching up to him. But going back to the OP's question, yes, you can build a PRIMO adult BMX bike with 26" wheels. Don't hesitate to do it...
I began riding BMX "circus bikes" with 20" wheels, but once I grew up to be an adult, I wanted a bike which fit my proportions better, and the Powerlite Cruiser was the answer. If you can find a Powerlite Cruiser frame (with Powerlite forks), buy it, dude!
You won't be disappointed! There's nothing wrong with a Powerlite Cruiser, even if the company went under or whatever... those Powerlite bikes were bulletproof! Nice and light too, so they soared over jumps! I miss my Powerlite Cruiser...