The survey isn't a request for people to send in a wishlist of features. Nor is it, like some DSLreports conspiracy theorists think, an opportunity to justify eliminating a service. They are just collecting user feedback on which already implemented GV features are most valued.
The strategic direction is to migrate and consolidate GV features into the Hangouts user interfaces. There is no nefarious plan to eliminate OBi access.
There is not going to be any further Google software engineering development effort at all on the old Google Chat/Talk related components. Specifically: no feature changes or additions to the Google Voice website, nor the mobile Google Voice apps. There is no point whatsoever in submitting a desired additional feature list that depends on the Chat/Talk legacy platform...it's not going to happen, guaranteed, based on my previous conversations with Google engineering regarding changes to those interfaces.
None of the suggestions listed above will likely be implemented, with the possible exception of the ability to record VM greetings via a computer on a web page vs. via a physical telephone number, because they depend on the now-obsolete Chat/Talk infrastructure.
There are some limited features for OBi users that could be added by Obihai engineering, not by Google, which would involve OAUTH 2.0 access to the user's account. For example, the 10x2 OBi phones can now access the user's Google Contacts, so that's one area that Obihai could leverage. However, calling features are limited to the narrow feature set included with WebRTC, which is focused on web browser-based calling.
If you want to submit useful input, simply mention in the comments how much you value using an OBi device with GV, and add it as an "Other" method for interfacing with the service.