Ah if you're not starting from scratch it's not so bad - I was under the impression you hadnt got a car yet.
I made my navigating debut in a Mazda 121 (kia pride) and everyone laughed. We came 21st o/a and 6th in class despite a crash on the first selective. It's nice to try an odd car, but if you plan on keeping it going it's cheaper and easier to go tried and tested.
Incidentally where did you get a weld in cage for a sunny from?
I'm not trying to cursh your dreams or anything like that, I just hope you can appreciate that rallying is much more than the spec of your car, and what is on paper a quick car is not necessarily a good rallycar.
Personally I'd leave the sunny as is, have some fun in it then if you do get to Arwel Sbidi level, then think about your car choice.
I'll volunteer to marshall if you need one up this end, I knwo how hard they are to find!