I admire your 'can do' attitude.
I am not sure that your idea is very practical.
Tent makers have put a lot of thought into the stresses encountered by a tent. I bought some no-see-um proof netting to patch various holes in my r-dome's mosquito netting. That worked. However, building something that keeps bugs out, especially along the skirt, while being strong enough to stand up to routine use, I am afraid would put you into the 'school of hard knocks' where you learn by doing, and repairing, and doing, and repairing, etc.
Lots of people recommend 'easy ups' as an intermediate step before committing to one of the side tents. If you really want a side tent like the r-dome, I suggest you also look at PaHaQue side tents, altho I have no information on how well they stand up to use, and there may well be others out there.
Good luck