this uses Brassica, a sound change applier, you can either run it locally or use it on a browser (which is what I did)

this was made in a day looking left and right for proto romance reconstructions and historical nasalization rules for portuguese, plus a bit of hackish manipulation to get things working, if I get interested in it I might tidy it up a bit more, here's an example of what it comes up with

"jẽolho" is an old form for "joelho"