? You're kidding right?
Of all the things one could use the Concorde for and for which it wasn't designed, the 'fast paratroop' option is probably the least needed, the least practical, the least likely and the most costly, considering anybody can see the Concorde is completely unsuitable for that because:
- it's too fast (you'll scatter your paratroops over 3 different countries and the chance of injuries is massive);
- no rear ramp for fast egress (you'll scatter them over yet more countries), the pole is a neat idea, but designed to exit a handfull of people, not 60ish heavily-laden paratroops as quickly as possible;
- max 128 passengers (which equals to what 60ish paratroops at most, which is equal to what a cheap, versatile C-130 carries);
- cost;
- not versatile;
- no refueling possible yet, so that'll need to be developed too, which'll cost you;
- it'll need to be redesigned for depressurization etc, opening a big door during flight isn't exactly in the original design specifications;
- I must have missed the need for a superfast paratroop carrier
Furthermore, designing an aircraft for dropping paratroops isn't as easy as it might seem. The C-17 had bucketloads of issues and wasn't cleared for paratroops untill after quite a delay and quite a lot of cost, and unlike the Concorde, the C-17 was actually designed to carry paratroopers.
The only possible use for the Concorde would be as a missile carrier, but even that's fraught with problems. I'd rather use the VC-10 for that, which would actually be a cheap, usefull conversion. However, the UK chose never to use them for that, despite buying quite a few on the cheap in the '80s.