I recently found another wonderful steal that I cannot refuse- a Power Trip Ronin ladies denim armored jacket. It's black, decently casual looking, and best of all they make it in a 'Diva' size (aka, plus size)... despite the fact that I lost 30lbs in the hospital, I am still maybe 15 lbs and at least one bra size away from being regular women's sizes (but I have lost a pant size, yay!)

Anyway, this will be my summer jacket! I'm quite excited about it. I want to waterproof it- even if I never go beyond cupcaking on Lokky's Stella again, that's his only mode of transportation and we take it anywhere, rain or shine. I'd prefer to waterproof this denim jacket- and I have some questions.
I've seen what Nikwax does- Nikwax helps reinforce things that are already waterproof or water resistant. This denim is not. So, I think I am forced to use a silicone waterproofer on it. I know that once something has been siliconed, stains/dirt that were already on it don't really come out- but that won't be much of a problem, I can apply the silicone when it's new, and it's jet black anyway.
My questions are things like this: will a silicone waterproof layer change the machine-washability of the jacket? (I know I probably can't put it in the dryer after I treat it) Will it change how I apply patches? Will it DRASTICALLY change breathability of the fabric, or just a eensy bit? Will it change how soft it is/make it rigid?
Do you guys have any recommendations as to a particular product, or way of going about doing this? Any cautions?
I had also planned on applying a silicone waterproof to my Prima saddlebags eventually... that's assuming we can maybe sorta salvage them, which I'm not positive of atm.