DCDCs usually limit current themselves, in fact that's often the main reason to install one even if the Vin = Vout
So should be no worries about OCP there.
DCDCs often work in scenarios where charge current is coming in while loads are being carried, one may varying, greater current than the other, swap places where going positive vs negative direction at the bank from one second to the next, no worries.
Not to mention the loads carried by the DCDC may be essential to operations, even safety, no?
I'm thinking you're looking for a solution in search of a problem.
I am thinking if regen generates say 50A, the battery takes 30A and DC/DC draws 10A, where does the rest of the 10A go? Would this be the only case where DC/DC would drain more current than it can handle and an electrical system to prevent this is necessary?
Remember, sources do not "push" current, just make it available.
Loads "pull" the actual amount they need.
So hypothetically, if regen is capable of putting out 50A, but the battery is at such a high SoC that it "can't accept" (won't draw) that much, then some power must be shunted to resistance or otherwise burnt off, or the braking power might be too low?
Think of a big 300A alternator in an ICE vehicle; with no loads it offers barely any friction resistance. Turn up a big enough stereo and suddenly engine power to the wheels is noticeably reduced, maybe a 20HP of physical load diverted.