[TYPO3-dev] Extend/modify flexforms from another extension?

[Ryan Hayle]

Is there any way to extend the flexform options of another extension? 
It doesn't seem like xclass will work for this.  I tried loading a new 
file like this:

$TCA['tt_content']['columns']['pi_flexform']['config']['ds']['tx_cal_controller'] 
= 'FILE:EXT:aba/flexform_ds.xml';

But that doesn't work since within the backend, I don't think my plugin 
code gets called if I'm editing the CE of another extension.  Also I 
have no idea if it would even be supported to have an xml excerpt and 
have it merged with the other.  Has anyone come up with a solution to 
this?  Can flexforms be modified with TS?

Thanks,
Ryan