Seems more hassle than its worth.
Configuring the keg, storing the keg with valve, sanitzing the valve, cleaning the yeast, etc.
I ferment in a sanke with just the stem removed, cleaning is easy. If you want to reuse yeast you can pitch on top of the yeast cake. Another way to make your yeast go farther is to make an extra large starter and preserve a cup of starter in a sanitized container in the fridgde.