I would really love to get the current YUI2 based form rendering replaced by Aikau forms and have been pushing the Product Management team to get this prioritized on the backlog. Ideally I'd like us to get to a point where we can store the form definitions on the Repository (rather than in Share configuration) and allow dynamic creation and modification of those forms. All the components already exist it just requires the allocation of resource to make it happen.
I think that customization an existing Share instance to do this would be possible but it wouldn't be a trivial exercise. The forms runtime is quite complex and it depends on how many of the existing form configurations you intend to honour with your implementation (of if you intend to just intercept certain forms). Unfortunately I haven't been able to spend enough time on this to give you much more guidance than that!
Regards,
Dave