I don’t think servos are used in decent gimbal since maybe 5-6 years
A 2020 decent solution for a plane facing down gimbal would involve 2 axis, brushless motors with encoders, storm32 or Alexmos. This is the bare minimum for a decent solution.
If you get exotic you can add coreless (low cogging motors) and vectornav sensors to make it better. If you plan to sell it for business do not forget to take in account people will want RTK geo reference to the pics.
So to make it short, i think you are trying to reinvent the wheel with ancient tech, you are i would say 7-8 years late to the party
We, for a living, take pics of 2mm serials on thousands of photovoltaics panels with a facing down Sony A7R IV camera, so i guess i know what i am talking about.
p.s. Gimbals are configured for specific cameras because they need to be balanced and with different cameras is very difficult to have a “one that fits all” solution.
p.p.s www.uavskies.com shows a strange page, maybe your web server has probs.