You want epic? I'd be up for a SoMo epic!
Between BV and Telegraph is the best part of National (IMO) - you must do it! It gets more techy and there's more exposure, but it's not that long so even if you have to walk lots it doesn't matter... but you must do it and see what you've been missing. Beyond Telegraph, National is less technical for the most part, but there is a big hike-a-bike to get out of Telegraph pass. On the far side of National it gets more slip-n-slide kind of techy, but nothing is too hard except for one really steep short section with nasty switchbacks. I do suggest wearing armor for all of this
Once on the west side of National, there are unlimited routes back. Here are some suggestions:
(1) If you've had enough... San Juan road back to Central - take canals and Baseline around to Pima Canyon
(2) If you want more... Roads up Buena Vista, then back on National, Corona Loma, or old Man's
(3) If you want lots more... Return on Bajada (or road) - up Ranger - down Mine Drop (or the Fuzz as some call it) and back on super secret trails with return to Pima Canyon on Desert Classic.
(4) If you want to go where few have gone before... Gila to super secret trails to Telegraph Trailhead to DC
And if you are really into pain, toss in an Alta loop, and do it ALL with flat pedals! I did that recently and was out for 9-hour 35+ mile adventure.