Getting here late, but yeah actually I think this would be possible, if you could manage to find a bottom surgeon who does surgeries for people who aren't transitioning. Unfortunately I don't know of any who don't require therapist letters or time on T, esp in the states.
Metoidioplasty is complicated in that you need to have a certain amount of growth in order to be eligible. DHT is actually what causes dick growth. A certain amount of the testosterone most guys take is naturally converted into DHT, and that results in penis growth. So theoretically, someone probably could just take DHT and experience growth. Whether it would be enough for meta or if it would cause other unwanted side effects is a question. This is all just theoretical of course, I've never heard of anyone who's done this.
I know for a fact it causes hair loss, which can sometimes be very serious. And that's only for the 3 month recommended time frame that guys on T take it for. You may need to take it longer than that, which could really do a number on your hair.
I think to be safe, you would also want to be in contact with a doctor for blood work, to make sure no bad side effects of the DHT are happening. I'm no doctor, so I really don't know what those could be, but I imagine too much build up of it in your system can't be good for you.
Pumping on the other hand, totally safe. Go for it. I've had success with pumping myself, but to be honest I doubt you would ever achieve enough size for meta with just pumping.
Phallo is a different story. You may want to consider that as well.
Unfortunately non binary transitions are sort of new territory in the medical world and the trans world. It's all pretty much up in the air, with very little support from medical professionals.
Your best bet though, is probably to check out one of those lgbt clinics in DC. You'll probably be able to find non-binary friendly doctors there who can help get you the information you need. And find a therapist that actually specializes in gender therapy. I found mine through
psychologytoday.com if that helps.