I put the cable inside the hose for mine. Problem solved.
Caveat emptor:
- for it to work, I had to make mini-holes in the hose and I did not cut into the braiding, just spread it out and pushed the cable through the opening, was tricky 3 hours work but that way the pressure/friction from the stretched hose and braiding is enough to fix the cable in place, not tape or any other fixing of the cable needed
- the cable becomes "tied" to the hose as the hose will have "holes" if cable is removed in future
- you cannot use the hose for any rough work - basically anything that can pull steel shavings, glass etc. that could cut/damage the cable
- to be safe, I used the "heavy duty" green cable from Festool which is way, way stronger/durable than your normal rubber one
- there is NO WAY it will pass any safety inspection, so no-go in a commercial setting
Overall I am sure it is safe with the heavy duty cable and dedicated to tool use only. But safety regulations do not work like that ...
All things considered, I am very happy with the arrangement.
It is a more comfortable solution even to the official Festool sander hose+cable combo. That was the main motivation actually as I did not like the hose-in-cloth setup.
One option, for those with the cable arm - the last section on it has a similar arrangement, but not sure how it is handled there where the cable goes "inside" the hose. Getting that hose only as a spare part might do the trick ?
EDIT: Found, unfortunately seems to be NAINA:
https://www.amazon.de/Festool-456746-Saugschlauch-27-antistatisch-m-as/dp/B004MN9IXG
Can someone who has it from the cable arm check how it is done? Is the cable "freely" in the air stream like I did or is there some other arrangment, cable embedded in the hose itself?