Hm, a sure-fire way to get the width you want would be a blank quad. You could run something on the preparse event to replace all instances of " " with "<q=mySpace>" for example.
I've considered adding kerning options for instances like this, but most of the time fonts are configured just fine, and I feel it's better to leave it open-ended for solutions that can be modified for different projects... But I should probably include a blank quad replacement script for situations like this, then!