Hmm -- I do not understand what is the use case for this. For best design, clearly, I'd use a proportional font. So whenever I want a monospace font, there are reasons that exclude proportional fonts. An obvious reason would be a grid that the letters need to be arranged in (for whatever reason). But then, I can only imagine that any smart rearrangement of letters out of their grid box will be unwanted, because it interfere with that grid. Instead, stupidly simple letter placement will be what I want.

I have an idea for an advanced technique that yields much better visual appearance (but that is also not want you'd want, for the same reasons): instead of just focussing on pairs of letters (so primitive!), consider whole words and optimise their letters' shape, width, and horizontal position, but keep the size of box of the word. I call that 'equilibrium texture healing'.