Most anything can be programmed, but in this case the task is very difficult. 

Modern fonts always use filled paths instead of stroke lines, so an “A” consists of two paths: the outer shape and the middle triange are separate:

there is no easy way to convert that into a dotted line that matches the ‘black parts’ of the glyph shape. Perhaps you could use two regular fonts: one sans-serif and one with dotted lines? There are some free fonts with dotted lines that can be found on the web, e.g. here: http://www.fontspace.com/category/dotted-line

Another option would be draw the ‘normal’ uppercase letter directly as a metapost path. In that case it would be rather simple to create a generic dotted path from that using ‘setdash’. However, without manual work, it will not look as good as pre-drawn font, because for a ‘nice’ dotted path you need to make sure that the dots in the crossbar of an ‘A’ line up nicely with the dots in the diagonal outer strokes, which is quite hard to do.

Best wishes,

Taco

Taco Hoekwater
Elvenkind BV