The subject says it all. Over a select region or an entire score, I need equal measure widths. I’m guessing the answer is “no”.
For me, this would be a great feature. I do a lot of very easy/medium concert band/string orchestras and my client has asked for this style - usually throughout a score, “whenever possible*”. Another client does “rhythm band” scores for elementary music classes and prefers this also.
*For the occasions when this is not desirable, when a given measure has to be widened a bit to loosen up spacing for smaller note values, it would be nice to be able to select that measure and add an amount (in spaces) to its width.
You would need to set the note spacing ratio to 2 in order to come close to achieving this, but I think this would be a bad idea: you will in general need wider spacing when using fully proportional spacing than you would otherwise. Provided you know that you’re never going to have a note shorter than, say, a 16th, then you may be able to set the ideal space for a quarter note such that it looks OK even when you have 16ths with accidentals, but in general the problem with proportional spacing is that it just doesn’t look right for most music – only music that uses time rather than rhythmic space as the governor of its horizontal dimension.