It is possible and relatively straightforward - you will just need to make sure that the person doing it uses a 'stretch' stitch otherwise the shortened seam wont stretch and the stitching will snap. This isn't difficult though and any decent alterations place should be able to do it for you.
I do that when i buy jods for yard normally the bargain pairs etc and just chop them off.
You can just chop off breeches though can you as the velcro will go as well.
I use Shires saddlehuggers breeches for day to day use. They come very long and I don't like jod cuffs, so convert them to shorter breeches with a pair of scissors. Jod done!