Currently there is no way to tell a tryjob to build an image out of a set of given CLs and test paygenbuild and paygentests for them. The only place this is done is in canaries and the only way to do it is to land the patches and allow the canary releases to test them. However, this is not an ideal solution. We can build payload trybots, but they only run the tests for previously generated official releases. 

It would be great to allow tryjob to build an image and run paygenbuild and paygentests (and possibly other normal tests like hwtest too) for verification. Something in the line of:

cros tryjob -g <some-cls> --paygentests --src_version xxxx.x.x board-release-tryjob

There could be restrictions on image signing, but we probably don't need to sign the images for this special purpose.