Relacing

any wheel can be relaced with stronger spokes but they usually have to be drilled out.

drilling rims for larger nipples is easy, as it's thin steel (or aluminum) and it punches right through.

hubs can be a different story, depending on the material it's made from. a hardened steel hub can seem almost impossible to drill out 36 spoke holes, but you just need the right bit. aluminum hubs are simple.

i do it all the time, and if you go this route, make sure you get the right size drill bits for your spokes, take your time, and clean off all the burrs off the rims so you don't get flats, and keep the metal shavings out of the hub.

Another thing you might want to be aware of is the length of the spokes. Schwinn S7 rims are generally laced with spokes that are anywhere form 1/8 to 3/8 inches longer than the spokes used in the standard rims. It depends on what cross pattern was used. I learned that many years ago as I was replacing S7 rims with the standard rims.

& yet one more thing to consider... I recently restored some 24" S7 wheels; I ordered new stainless steel spokes the exact same length as the old ones, (thinking 'how can I go wrong?')
Well... the spokes were the same length, but the old nipples were longer than the new ones, so the new ones were too short & I couldn't find longer ones anywhere. (thus, I had to order new spokes 3/16" longer than the originals!!!