Try through caulking.You can get latex and acrylic and silicone caulking.

Not cheap but reasonable prices, ~$200 for a larger framed canvas or acrylic print. 

Any smaller cracks fill with siliconized acrylic latex caulk.

@Bob S.I always paint the inside usually just the same color. acrylic cabinet paint

You can't fit them thru a typical 24" bathroom door on a remodel.You can still do the acrylic surround, you just use the one where the tub and surround come separately.

Also, lookup the difference between Acrylic and Rotomolded tubs.

Acrylic tubs never rust.10.

We thought of having it converted to a one-piece acrylic or fiberglass shower and called Home Depot.

There is no way I can install skylight  Some sun tubes can be routed, look em up  https://www.homedepot.com/p/VELUX-14-in-Acrylic-Dome-Sun-Tun...This is 1 of the more common ones, there may be others IDK.

Compare the materials.... plastic, acrylic, fiberglass, tile, porcelain, enameled cast iron, etc.