Yes, the windows can be replaced. Thor/Damon/Four Winds used standard sliding Hehr windows for years.
The new "all glass look" sure are pretty but seem to have some drawbacks - like mentioned.
The swap should be easy if the window opening is a standard size.
After a swap, the old windows could probably be sold to off-set the costs.
Please notice there are single and dual pane versions of the same windows made by Hehr.
Hehr is sold at RV suppliers and on-line like :
Hehr windows, Hehr International, RV windows
Kim and Steve, Mustang LCDR (Ret), '07 Damon Outlaw #1193
I have seen gross intolerance shown in support of tolerance, Samuel Coleridge
WE LOVE OUR OUTLAW RV