I will have to add them specifically for you (when I install them, or after the fact for you since you already have some) to enable/disable them, but yes it should be possible. There are now 2 templates to choose from when creating a server: default (the existing one, PLUS the Plugin Selector), and a flatworld that I've yet to add any plugins to. @Nick if you want, I can add the Plugin Selector to your existing server, since you had me upload your map, just let me know.
Coming Soon to Cupcakes: Select From Pre-made Cupcake Templates, each with their own plugins, world style, and more. On certain templates, you'll be able to enable and disable plugins to your liking through an easy GUI:
Yes! Cupcakes include the plugin "Essentials", which has it's own economy setup. The global economy is not extended to Cupcakes, since you get OP. With the Essentials economy and you having OP, you essentially have control over your own private economy.
We used to have a sign board at the survival spawn for things like this, but it was rarely used for it's intended purpose. I like the idea of players posting jobs for others to do, but it would have to be a custom plugin.
In the past we've talked about adding a second creative world, with flatland + plots instead of open terrain. How do you feel people will think about that?
I don't think I'd ever remove the current creative world, but I wouldn't be opposed to moving the spawn point elsewhere to get a change of scenery and more people a chance to build around it. It is entirely too much work to move things over to a new world. People will lose things anyway just because they had homes set at old coordinates, or they're gone for a few months and come back and their build is gone, etc. Too many problems arise compared to the problems it solves.
Farms must have something built on it related to farming. More info on plot rules can be found in this post:
I don't know which plot you're referring to specifically, but note that plots may not be empty even if they appear so. Some people extend their farms underground and never touched the surface of an adjacent plot, or they seal it up with dirt/grass.