I mean, yeah. It's always possible.
The only real limitation there ever was, was him saying that his regenerative powers have little effect on others.
If "sacrificing" himself is what allows them to have a larger effect on others, then I think it's totally fine.
Or maybe he simply losses...
If he did enough to King, then Zoro at 30% should be able to take him down.
Hm...how about this scenario:
1. Marco keeps fighting King and continues gaining advantage. Meanwhile, Chopper begins healing Zoro. Who knows, Hiyori might show up and help out, too.
2. King becomes incensed and decides to access the CC Poison Gas that Jack used to wipe out the Minks (this will also let us see what it looks like in a real-time fight after years of only being told of it).
3. As you said, Marco's regen power only has little effect on others, so he decides the best way to prevent a massacre is by fighting off the poison gas with his blue flame, let's say by absorbing them and regenerating repeatedly.
4. Oda already said that Marco's regen is limited up to a certain time slot, so this is where the limit kicks in. The poison gas kills nobody, but Marco is incapacitated.
5. King delivers a decisive slash to Marco.
6. Before Marco loses his consciousness, he gives what is left of his blue flames to Zoro. This, plus the previous treatment, restores Zoro to somewhere between 30% to 50% health or heals up half of his broken bones.
7. Marco finally passes out.
8. King tries to finish him off, but is stopped by Zoro.
9. Zoro pimpslaps King to oblivion and rejoins Luffy to defeat Kaido for good.