So for those wondering why there's no Crystal, I have a pretty good idea why. In Japan, Crystal has a building called the PCC (Pokemon Communications Center) that used the Mobile Adapter GB to connect to dialup servers and essentially worked like the WiFi features in Gen 4. Now, with how they mentioned they didn't want to do Gen 1 without being able to trade, they probably also didn't want to do Crystal without its biggest feature possible.
Now for other problems:
- They can't cut the PCC in the Japanese games because it's where you receive the Odd Egg and Eon Mail.
- While most of the mobile features were translated into English, they definitely weren't for the other international languages.
Either way, it would be too much work for a VC title.