Manual Hubs

Well, you could. But you'd have to redesign the front wheel hub assembly and do it in such a way that the axle stub-shaft is supported at the spindle and also so that it would fit an existing set of manual hubs. I guess if you're creating one-off parts for the bearings, you could create your own one-off manual hubs, too. And some wheels with a big enough center section opening to get to the hubs...

I wish we had the option. I suspect it would give back 1-1.2mpg when unlocked just from the lowered rolling resistance.

Technically, it's not too tough. The 1985 and up Toyota pickups had independent suspension and manual hubs. If you built the bearing assembly correctly, it wouldn't stick out a whole lot but would still allow for unlocking and locking.

I'd take manual hubs in a New York minute. I drove all over the southeast with manual hubs most of my life (this is the first 4x4 truck I've had without them) and never had a problem. I'm not a fan of vacuum hubs, for sure, but a good manual works simply and surely, in my experience.