Ok, so this will break many saves, but it might be worth it.
1: Better saltwater
Instead of there being only 2 levels of "saltyness" in water (SLTW and WATR), SLTW should use a property to keep track of how much salt it holds. This will prevent salt duplication (SLTW+WATR->2 SLTW, 2 SLTW + heat -> 2 SALT + 2 WATR)
2: Conducting SPRK & Electrolysis.
In real life, pure water doesn't conduct electricity, unless it has salt or other things in it. WATR in TPT shouldn't conduct electricity (because its resistance is so high that any electricity would only travel a short distance), and SLTW should conduct differently depending on how much salt in it. Also, sparking saltwater should convert it into HYGN+OXYG, instead of having water SPRKed by IRON. To prevent entire areas of water being electrolyzed by spark loops, SPRK should travel a certain distance before stopping.
Maybe there could be a flag set in older saves, to keep them from breaking.
This idea is great! It's going into a new mod I decided to make!
The second statement is kinda wrong, water does not conduct electricity only if its pure water (distilled water, DSTW, pure H2O). If you grab freshwater (WATR) from a pond, faucet, well, etc, it will have lots of dissolved minerals and other stuff that will give it conductivity, and if you measure its resistance, it will be high, but not infinite (let's say 500kOhms/cm). You can electrolyze freshwater using higher voltages than those used to electrolyze water+salt (or any other electrolyte). It has no salt (NaCl) in it, but this does not mean that it's not conductive.