I don't recall off the top of my head how thick the cylinder walls are on a 25, but I expect the answer is no-in that case. The sleeve has to be thick enough to take the stresses involved and retained by a flange and a shink fit to keep it in place. If you machined the chamber throats large enough to allow a sleeve, there wouldn't be anyplace to have the flange-unless you did sleeves for each chamber (and if the cylinder walls would be thick enough to retain the sleeves). It'd probably be cheaper to machine a new cylinder.
The late George Nonte used to be real big on chamber sleeves for autoloading pistols to change calibers or save a barrel with serious chamber problems. There the existing chamber was bored to an acceptably larger diameter and to the depth of the original chamber (or possibly longer if the new caliber was longer than the original.) A sleeve would then be machined on the outside diameter (a very slight bit larger than the hole it was going into) to be a shrink fit into the barrel. The sleeve would be chilled in dry ice and the barrel slightly heated (shink the insert, expand the barrel bore) After the temperatures had been equalized, the sleeve could then be finish reamed. The forward shoulder of the sleeve bearing on the shoulder formed in the boring process retained the sleeve against the pressures and bullet forces. Silver solder could also be used to help hold the sleeve in place.
After a certain amount of thought, it just might be possible to bore the cylinder face to allow throat inserts to be silver soldered in place, then faced off and reamed. I personally wouldn't do so. You currently may have a working firearm that isn't as accurate as you like. You might well end up with a paperweight.
You'd probably be better off trying to find a compatable cylinder of a smaller caliber and getting it rechambered.