Creating a custom adaptive form component - that will submit and store data

Is it possible to create a new adaptive form component in HTL/sightly or extend an existing component?

Basically just trying to create a dropdown component (or any other component) that populates its values from a java model and will be saved to crx repo when the form is submitted.

All current adaptive form components are written in jsp and I've already tried extending the GuideField class them and manage to populate a dropdown dynamically but on page load it displays this in the console and the submit button won't work.

guideRuntime.js:26192 TypeError: Cannot read property 'priority' of undefined
    at child.getAttribute (guideRuntime.js:26698)
    at child._addProperty (guideRuntime.js:30187)
    at child.<anonymous> (guideRuntime.js:30156)
    at en.js:576