No reason in the world -- go for it. I used every pin of a 15-pin D-sub connector but did not combine grounds (which I wish I had done to reduce the bulk of the cable).... Any reason to not use a 25 pin DSUB ... ?
A removable pax stick with the wires hanging out of it is one thing. How about the pilot sitck? If you ever need to replace a switch in the grip, it would be much easier to work on it on the bench. But how do you plan to pull the wires out of your stick if you have either a Cannon or D-sub hanging on the end of it? I put D-sub sockets on all the wires coming off the stick grip and pins on all the airframe wires. Connect them one at a time and individually heat shrink them and they will be fine until they need to be separated.
Ed Holyoke
I used CPCs (circular plastic connectors - inline male/female) for my infinity grip. Works well, and is relativity compact with plenty of conductors. The connectors use standard dsub pins and sockets.
I put D-sub sockets on all the wires coming off the stick grip and pins on all the airframe wires. Connect them one at a time and individually heat shrink them and they will be fine until they need to be separated.
Ed Holyoke