thanks for your suggestion. We have discussed the issue of combined Update Queries with SELECT parts at the group's recent face-to-face meeting. The group has resolved at this stage to go forward with a design where Update queries can only return success or failure .
Although the general spirit of your proposal combining query parts with updates is interesting, we will not be able to take this extension it on board with the resources and time remaining, following the group's charter. 
with best regards, Axel, on behalf of the WG