Allow to change the iframe rendering to vertically align inline macros

I'm currently creating a Confluence Connect add-on which makes use of dynamic content macros. Some of them are intended to be inline macros ("outputType": "inline"). Unfortunately, their content is not vertically aligned with the surrounding text because the generated iframe does not have "align=middle" set (or the HTML5 equivalent with CSS).

As an example, see the attached screenshot where "Hello world" is the output of my dynamic content macro (note that I've set the size optimally with AP.resize, otherwise scrollbars in the iframe would appear) which is not aligned with the surrounding text.

A possibility to change the rendering of iframes with Connect (beside setting their size with AP.resize) would greatly help here.