>>26661251>>26668341https://github.com/pret/pokecrystal>>26661807There's definitely enough space for it, ROMhackers are able to find plenty of free space on the ROM.
The reason Kanto got truncated isn't space, but rather time, GS was already in development hell and I don't think they really wanted to delay it even further porting every Kanto location. Imagine if S&M got announced last year but had the same release date as now, and we only had slightly more information than we have at this point of time, and then it gets delayed 2017 after that. The entire reason Yellow exists is because they needed a filler game in Japan.
That being said I don't know why they didn't re-add locations in Crystal, unless it was just laziness.