I have actually been working on a system with mechs for my Gundam fan-server, at the moment I have it so that players can enter a pre-defined schematic of a "Mech" machine (it's really just an invisible horse which has it's elevation raised so it looks like you are sitting in a pilot seat of a mech) and drive it around and fly it using it's machine guns, rockets bomb etc, all this is done using Skript and some homemade java plugins. Just keep trying to think outside the box of the "Usual" minecraft, but don't commit to it just because it might be easy
Back on-topic, I do like your roleplay server idea more than the Pixelmon server, I have seen too many pixelmon servers come up and the only new ones that I believe could survive and actually get a good playerbase would be the ones that are in "OfflineMode". And if you do a roleplay server concept please do not just make it one giant complete thing right off the bat, Players love to come into a new server and see it progress as they play and advance, thus, building a good a playerbase. :3
