Ok, thanks.

So, I could basically rewire it, I guess? There is even the original cable of one of the joysticks in the box, with the connector on one end. Some Famiclone joysticks can be opened, though most recent (post 2000 ones) have some built-in IC. I'm not sure if it would interfere with Rambo's operation.
The next thing to sort out would be - the price negotiations.

The model on offer is with 96 built-in games. It interests me primarily because I've used many famiclones, and I noticed these built-in games are similar to ones I know but still somewhat different - would like to see them in reality. It is a vintage console, I can tell it by the amount of electronics inside (board spanning edge-to-edge inside a console) - famiclones typically have just one chip (NES-on-a-chip) and up to about 10 other components if they don't have an RF output.