Moncrieff and others said that lack of definition could give states substantial leeway in tackling the subsidy issue, without having to necessarily build a stand-alone exchange from scratch at the cost of tens of millions of dollars or more.
"I think there are lot things that will work," Moncrieff said.
H. Guy Collier, a lawyer in the health practice of the firm McDermott Will & Emery, suggested that one potential solution is for a state to formally declare that the state has established an exchange, but then contract out all of the functions of that marketplace to HealthCare.gov.
"There's a possibility they could do that," Collier said. But, he added, "It's not free from doubt."
In advance of Tuesday's dueling appellate opinions, Obamacare blogger Charles Gaba, who has been tracking enrollment in exchange-sold plans, wrote an article with the headline, "I can save the Affordable Care Act for just $360.00!!"
Gaba wrote there is "an incredibly stupid-sounding solution" to the problem of a potential Supreme Court ruling invalidating the HealthCare.gov subsidies. That solution, Gaba said, is having each of the 36 states spend about $9.95 apiece—or less—on website domain names that would say things like "HealthcareAlabama.gov," or "HealthcareAlaska.gov."
"Then, just set up those domains names to repoint to the appropriate subsection of HealthCare.gov," Gaba wrote.
Gaba suggested that would be enough to have a state "establish" an exchange, without actually having to do the heavy lifting of enrolling them in coverage.
Moncrieff said that idea is not as harebrained as it might appear.
"It's possible that, yes, you could set up a fake portal website that redirects to HealthCare.gov," she said. "It's possible that this could be a very cheap, easy fix."
And even if that solution wasn't legal under the ACA, it could take years of new litigation to resolve that question—which would keep the subsidies flowing, she said.
Holtz-Eakin said there might be an even cheaper solution.
Read MoreCourts could cause big Obamacare $$$ hike
He said the federal government could make "36 copies" of HealthCare.gov's software, "and sell them for a buck apiece to the states affected."
For now, however, the Obama administration is hinging its hopes on getting the D.C. Circuit to reverse the panel's ruling that declared the subsidies were illegal.
The White House declined to comment when asked by CNBC whether federal officials were considering any workarounds to the subsidy problem if the Supreme Court takes the case and rules against the administration.
That didn't surprise Holtz-Eakin.
"I don't think they're doing anything right now" in terms of a workaround, he said. "They're going to make sure the money keeps flowing, and they're going to look at this in terms of erecting a legal firewall ... any public movement to explore these ideas suggests the courts are right, and they're not going to allow it."
—By CNBC's Dan Mangan