Flour labeled as Cake flour usually is weak flour: low W value, or less formally "low protein" or "fewer gluten". This is somehow weird, as some cakes will require weak flour, whether others nedd strong flour (for yeasted dough cakes, if they add lots of fat/oil to the dough, if they add lots of sugar, pieces of fruits/nuts, etc).
I specifically don't know whether Maida is strong or weak flour, despite this answer and it's comments.
Wheat plants has been selected for several milleniums to get more productive varieties, and, yes, grains that give stronger flour.
Substitutes as weak flour
Trying to get flour from a more "primitive" variety of wheat, such as spelt, emmer or einkorn. These are expensive where I live, and usually sold as bio, but maybe spelt is easily found in India. As they have not been so "genetically selected", they still have less gluten than today's "normal" flour. They also tend to have more and better taste than "normal" flour.
Another flour with low gluten content is rye. It has a different taste than wheat, but I thing it fits really well with cakes. This grain grows better in colder climates, so I'm not very sure how hard will it be to get it where you live.
Other flours, as rice or corn / maize have no gluten. It means gas bubbles won't be trapped in, and will result in a much too dense crumb. You might search some gluten-free bread tricks to solve this.
Substitutes as strong flour
Any bread flour will probably work. Maybe it won't rise as much and you'll get a crumb with a denser consistency, more similar to a "chewing gum" than a "soft cake". But if you are ok with this, you can go on.
Note(Thank to @Anisha for the suggestion):
Notice that different flours have different absorption, so some readjustment on hydration should probably be made to the original recipe.
You could substitute any flour you like, the purpose of the coating is to give it some extra crisp when frying. I would suggest maybe rice flour or you could use whole wheat flour but the taste may be different.
IMO, I would skip that step altogether though. A potato wedge is just a french fry cut in a different shape and we don't dredge french fries.
Best Answer
Most western substitutes call for using Corn Starch instead since the two have similar binding properties. For example see this:
http://www.buzzle.com/articles/tapioca-flour-substitute.html
Garri/Gari may seem closer to home, since it made from Tapioca as well (aka Casava), but it is a different composition than Tapioca flour. While Tapioca flour is primarily starch, Garri's composition is somewhat the opposite since Garri is what remains after the starchy water is drained from mashed-up, oiled Tapioca.
As suggested, look for starch-based flours, your best option is Corn Starch available in most countries.
Sources for my research:
On Tapioca Starch: http://www.bobsredmill.com/blog/healthy-living/what-is-it-wednesday-tapioca-flourstarch/
On Garri: Wikipedia :)