I love enthusiasm, I encourage it, but take it from someone with 20 years motorsport competitive (in Corolla's) and admin experience, it won't work.
Gemini's have been a great series in both track and rally, but their time is approching rapidly. This year was the last year for the Gemi's in Qld rallying, and I'd say their track life would counted in a handful of years.
IF you plan to run a series based the Corolla, you need to look at what made the Gemi's so popular. Ease of purchase, ease of parts, cost of parts, ability to buy $500 car, cage it, race it. The more restrictions you put on a class, the harder it is for first timers to enter. ie: 4AG + T50, not readily available for RWD without paying 2 x value of car, not OEM fitment meaning mods to fit to car, plus uprate diff etc..... First timers will be your core market, and you need to make it as simple as possible for them to enter.
What are you going to offer sponsers? In these times sponsers want value for money and exposure. You have to ask who outside a very (relatively) small community nobody will give a rats.
Excels are replacing Gemi's in the rally world as we speak. Cheap, modern cars, reasonably robust and a car people can relate to. If you want money, you need to go modern.
In all honesty, watching Corolla's at Willowbank would send me to sleep. Watching Corolla's at Lakeside would only be good for the carnage. They're handy at Morgan park, but like any track work, kW's are your friend. And if you don't keep a lid on mods, they with the biggest cheque book will win.
Which will be the case in the long run anyway.