The open-source plugin's only weakness is that it uses the v1 apis. I have been at this juncture myself. Grafana Enterprise wasn't an option - so decided to see how easy it was to write your own.
I built a plugin using the v2 API but not really any of its new transform features. So it did what a plugin using the v1 APi could do - but was much easier to implement. It took 2 days to prototype and about 2 weeks of tweaking. I was unsatisfied with a few aspects of it, and ultimately decided to just move on to other things.
I would say that writing your own would require strong development skills - especially problem solving and debugging - unless you are already familiar with Grafana's internal architecture.
