Allow custom microflow input parameters when calling from a page

It's probably been mentioned a couple times already, but if not...

I regularly run into situations where it would be very handy to be able to pass at least one additional parameter when calling a microflow from a page. 
For example, I have a microflow that I want to call from several different pages (or different places on the same page) and depending on the source, it needs to be handled slightly differently. Now, I need to make an IVK microflow for each page that adds the 'source' parameter and then calls the main microflow. That's a lot of extra microflows, where actually I'd want to pass the parameter in the request.