Understanding Double Dragon (NES)'s Level System

[RagingRowen]

So 0040 in the memory is the Level you're at, and I also found out that the starting level is set after the intro cutscene and the mission screen appears.

I set a Write Breakpoint there, and when the mission screen is about to appear it detects something at 1F47E, where we find a Hex 00 at 1F480.
I changed that to 01, but it instead just skips the Mission Screen. 
I didn't get any luck changing other nearby 00s.

I'm looking at this becuase I'm thinking of making a hack that makes it more arcade-like and in-line with the other games by giving you access to all moves from the get-go by putting you at the Max Level from the start.
I'm wondering how I go about locating how it gets your starting level number. Hopefully my searching attempts will motivate other attempts.