Hello Dr. Till,
Not to dissuade you in any way, but you are facing a tall order with the items you wish to accomplish and for a car with little support in the aftermarket.
Your best bet would be joining this forum https://www.impalassforum.com/vBulletin/10-caprice/
It's specifically for GM 91-96 B bodies. There's a decent amount of activity on there due to the strong Impala SS following. They might have more empirical knowledge on new aftermarket support for the '94 Caprice.
As a side note, I've owned a '91 Caprice Classic, put 300K miles on it, then owned a '96 Impala SS for 10 years and the wife stills owns her '96 Impala SS after several years of ownership and its her daily driver still.
The main problem is age with these cars, especially pertaining to the interior. There is little to no support I have found in interior part replacements. Also GM used the cheapest plastics and even though her car is garage kept and babied the interior is just falling apart. Plastic cracks all over and more rattles than I can care to think about. Just as a comparison contrast we also have a '94 Grand Marquis LS and the interior looks brand new, no cracks and no rattles. It's quite obvious Ford used much better materials for the interior than GM did in this time period.
My advice for power windows would be to hunt down the OEM parts. Whilst my 91, 96 and wifes 96 had/has power windows I am converting my beloved '73 Caprice Classic to power windows as well as 3 late 60's full size Fords (galaxie 500XL, LTD and an XL). The aftermarket power windows (non vehicle specific) are all junk in my opinion after an extensive evaluation of popular generic kits. There are aftermarket places producing vehicle specific power window systems but typically they run around 1000 dollars or more.
I actually bought another parts car '73 Caprice Classic pile of junk that still had all its power windows in it and was able to obtain the window regulators, brackets, etc.
You may have to do the same if you want a reliable power window system.