It’s definitely feasible. I’m not sure if your goal is to have a project that will stretch your design skills, or to have a working pen plotter.
If you’re interested in designing and building your own machine, then this is a good project to do that. I would definitely take a look at some of the other machines out there to see what they learned and try to incorporate that. But ultimately, drawing with a pen with a few stepper motors should be an achievable goal.
If you’re interested in just getting a plotter, then you should look at what is already out there. There is a lot of knowledge and experience soaked into those designs that won’t be completely obvious when you start. The cantilevered laser engraver would be a good one to try. Or there are a bunch of open source machines. A lot of machines that @dkj4linux uses for needle cutting would also be good. Or, just make an MPCNC 
. The axi draw is a pretty popular machine I see on #plottertwitter.
I also made some chicken scratches on how to make something like a corexy cantilevered design at one point. But when I think about how to actually route the belts, I think may be some problems there.
I totally understand the idea of making your own design though. Even if it doesn’t work well, it’s yours.