I've been away from pixelmon for a while so what I'm about to write might be inaccurate. The Suggestion involves Gymleaders. I've been playing for 3 days now and I've seen a lot of people wanting to beat the rock gym leader. In the time I've waited I have EV-trained 6 Pokemon and lvled them to lvl 20 (without training grounds cause I didn't know about them). He/she might be busy for all I know so I don't wanna sound judgy or anything.
My suggestion is this: Replace the first 3 gymleaders by NPC gymleaders. This was possible in the old Pixelmon, this way the trainers can progress through the first 3 gyms at their own pace and starting from gym 4 use the gymleaders you have (you can even put double shifts for the timezones on the next 3 so all gymleaders can stay). If you want to toughen the first 3 gyms cause NPCs are too easy you can always just pass the EV cap on their pokemon ;).
Get back to me with feedback and/or improvements