I like this kind of challanges.
I actually do exactly the same thing myself. In SR 2020 I've only done it with Serbia so far. My mission was to conquer Bosnia as fast as possible. Usually I use some houserules to make it even harder for me. One of those houserules I used were that I couldn't activily conduct diplomacy but only react to other nations suggestion. Also since for me this was just a pure war mission I could only order the resource and economical ministers what to do and not do anything directly myself. Also in this challanges I have to DOW Bosnia the very first thing I do.
Oh and I used the starting units since the mission was how fast can Bosnia be conquered by a human Serbia with the existing units. My record is that they gave up on 13th january at 04:00 in the morning... I played 3 times. (Yes I'm no good.) Oh and I don't use obvios exploits that the AI has not been programmed to understand. I do use orders like bomb units even though I know it's more effecient to do it otherways.
Anyhow I think I will try your challange... but be prepared.. .I'm a lousy player and I will probably not be able to beat you.