I've built a number of small frames for my late wife and a close friend, both were 5'1" to 5'2" tall. Some were Terry style with a 520 ft and 622 rear wheel. A couple have been dual 571 wheels.

You are right to think about the lugs being a challenge. Specificly the DT lug and the sockets on the shell will shift a few degrees from the 700c norm that every lug or shell I've seen are assumed to be for.

But the lugs and sockets can be simply bent to fit. Or you can cut a slice in the lug to allow the angle to spread then fill it in with brass. On my bikes I used Omar's bending bars (on the main tube sockets, thick walled tubes for the stays) and a lot of blacksmithing then I brazed the DT lug and shell sockets with brass to insure that any gaps weren't a problem. Took a bit of clean up and thinning filing to look good.

This and other reasons are why I've decided to do more with fillet brazing. A lot less prep, any angle can be done equally easily, a different look then the common lugged or TIGed frames that abound. Andy.