I think the answer to those inquiries is on page 14 and 15 of the Hollingsworth opinion: if you want proponents to be able to defend initiative measures in federal lawsuits despite the governor's preference to the contrary, you need a statute deputizing the proponent for that purpose, akin to the statutes authorizing private attorneys general in qui tam actions, complete with some modicum of control and a fee-indemnification provision.
Look at what the Court says:
We recognized [in Arizonans for Official English] that a legislator authorized by state law to represent the State’s interest may satisfy standing requirements . . ., but noted that the Arizona committee and its members were “not elected representatives, and we [we]re aware of no Arizona law appointing initiative sponsors as agents of the people of Arizona to defend, in lieu of public officials, the constitutionality of initiatives made law of the State.”
[The California Supreme] Court never described petitioners as “agents of the people,” or of anyone else. . . . All that the California Supreme Court decision stands for is that, so far as California is concerned, petitioners may argue in defense of Proposition 8. This “does not mean that the proponents become de factopublic officials”; the authority they enjoy is “simply the authority to participate as parties in a court action and toassert legal arguments in defense of the state’s interest in the validity of the initiative measure.” That interest is by definition a generalized one, and it is precisely because proponents assert such interest that they lack standing under our precedents.
And petitioners are plainly not agents of the State—“formal” or otherwise. [Petitioners claimed below that i]t was their “unique legal status” as officialproponents---not an agency relationship with the people of California---that [provided them with standing].
More to the point, the most basic features of an agency relationship are missing here. Agency requires more than mere authorization to assert a particular interest. . . .
If the relationship between two persons is one of agency . . . , the agent owes a fiduciary obligation to the principal.” But petitioners owe nothing of the sort to the people of California.
Finally, the California Supreme Court stated that “[t]he question of who should bear responsibility for any attorney fee award . . . is entirely distinct from the question” before it. But it is hornbook law that “a principal has a duty to indemnify the agent against expenses and other losses incurred by the agent . . ." If the issue of fees is entirely distinct from the authority question, then authority cannot be based on agency.
Hollingsworth v. Perry, __ U.S. __, No. 12–144, slip op. at 14--16 (2013) (citations omitted).