Well i know little about airoponics but I do know one small mother should supply you with about 15 cuttings a month .
No need for four of them unless they are differen,t strains that you like to keep.
I also think you are being a bit optamistic about your rooting times of two weeks and veging time of two weeks , I would say a month for each, twice as long.
But your idea is fine , if you get it all up and running without problems you should have a harvest every two weeks .
The only bastard is having to flush the ripe ones with fresh water so you will have a full time job flushing them by hand or changing em onto a seperate iragation system.

And to your other question i suppose you would have to get a comercial system to be any bigger as all these are for cultivating in a cupboard or a closet.

Looking after a mother is easy just look after it like you would any other plant food water light . A few days b 4 taking cuttings it is recomended to give a high N diet.

My mothers are kept on a high N diet .
If i want 10 cuttings i take 15 and trow away any that are shit and keep the rest.

Don,t expect it to run like clockwork .

Good luck
Disco........