This feature (
https://github.com/cryptonomex/graphene/wiki/design-issues#voting) would help with that a lot in BitShares 2.0. If that isn't supported (and I don't know why it shouldn't be since it is a relatively simple tweak), it can be approximated (at least for voting with BTS stake) using a zero pay worker proposal.
As for voting in the current BitShares 0.x system on the upgrade to 2.0, wouldn't it be easier to just have all the current delegates (and delegate candidates) publicly announce their position (for upgrade or against upgrade) and let the stakeholders vote them in and out appropriately over the next month? That way if the stakeholders are against the upgrade (which I don't think anyone believes is true), BitShares 0.x will have the right block producers in place to avoid the node upgrade that would cease block production by a certain date. I'm a fan of letting the elected representatives just do the right thing but allow the stakeholders who actually care to veto their decisions (and quickly vote them out) if they disagree. For example, I think the 2 week delay on delegate actions in BitShares 2.0 strikes a great balance between progress and stakeholder control when considering the reality of voter apathy.
Edit: Then again, this is a huge change. And in BitShares 2.0 any hard forking change should require active stakeholder approval. So I guess what you are proposing is the same thing. Plus, it is a easy thing to do, so why not. Let's see how long it will take to get upgrade-to-bts-2 voted up.