That sounds very promising. Do you have a time frame for this release?
It should be noted that we plan to make the ui an optional part of Aloha (with default being a jqueryui implementation) to make it easier to integrate into existing systems. The heavy extjs dependency is part of why Aloha is so huge.
I also plan to look into using google closure compiler in ADVANCED_OPTIMIZATION mode to shrink the size to the absolute minimum.