I don't know the formula for equivalency between multiple smaller gauge wires and one larger gauge. I'm sure there is a way to calculate it, I just haven't seen it. But to answer your question, yes, what you're proposing is correct, but I don't know the actual gauge wire(s) you will need.
The question I have for you is, how did you determine you need 2/0? That is VERY heavy. You will have voltage drop when running low voltage/high current (as drawn by the starter motor) over distance, but that seems way overkill to me.
I did the rear-mount battery on an old Mopar I'm fixing up and to figure what I needed, I used a clamp on ammeter to measure the current while cranking. As I recall it was about 190 amps. I don't remember off the top of my head what gauge wire I used but I think it was single ought, aka 0. I can confirm that when I get home and look at my notes.
Something to keep in mind with wire ampacity is that it's rated for continuous duty. In other words, the max rated current non-stop. Starters don't work that way, and while you don't want to undersize because of the voltage drop issue which will give you a slow crank, there's no benefit to oversizing.
The problem you may run into with multiple wires instead of one larger one is that the terminals are not designed to crimp onto more than one conductor. I'd be worried at least one would wind up insufficiently crimped. Also, use welding cable for the best results. It uses a very fine strand that will give the least drop and will be very flexible and easy to route.
If I have time tonight I'll post up some info and pics of what I did on that old car. The take away there being if 0 cranks over a small block V8, you should be able to get away with something smaller considering a smaller starter and a shorter run. But again, I'll confirm what I used.