Yes, I have replaced many sets of these pouches with pouch leather.
It is easy and only takes about a day if you pull the plastic rings
and glue the pouches on all of them before you return them to their
holes.  You will also need to replace the rubber valves as well, in
90 percent of the cases.  Someone will likely mention the guy in
California who supplies these valves as his name escapes me now.

The big problem I had, with only one of these pianos so far, is the
ribs on the soundboard do not go all the way to overlap the rim --
they are an inch or so short of reaching the edge of the soundboard
and the one I have has cracked the board all around the edge.  It will
require me to remove the board and put in new ribs that embed into the
edge of the soundboard rim.  It may just need a new soundboard, which
would be easier but probably not cheaper.

Doug L. Bullock
http://thepianoworld.com/