If I were you, I would swap the handlebar; I'd go for a MTB bar cut to size but I understand you are told and may require something for tall people.
Saint John Street cycle have many good choices and even if you do not purchase from them, having a good look could give you some ideas.

When it comes to other bikes, you will not find something that folds as well as a Brompton. if it is not and issue, look for Tern/Dahon and all the others that use their frame design (Raleigh in the UK had one, Bickerton is the same). The advantage of these is that they use std/generic components and mix them to a 20" frame. much cheaper to maintain and easier to source.

alternatively, look at kinetic, https://www.kinetics-online.co.uk/fo...ikes/brompton/, they provide some good custom mod that may suit you and allow your Bromptons to get a new life.