Agreed with Newt - the solution is to crowdsource a plugin. We could look at getting a form of community pot/ plugin bounty going?
The issue as far as I can see is that then we'd have the following problems:
A) Both Scirra and Spine could disavow the plugin as being developed by a third party
B) We would be beholden to the third party to update this plugin
C) The cost of outsourcing programming at a fair hourly rate would far eclipse the cost of the tools themselves
I guess we can only appeal to the cold heart of capitalism and hope that an enterprising dev sees that there's market demand for this plugin (and that he/she then sells it for a compelling price)