I used to run shieldless on my T-9, but a bad experience changed my mind on that. The thing you have to remember is that your FSD upgrade lowers the integrity of your drive. I was interdicted by a python and he knocked out my drive instantly. Thank god for reboot.I really love your shieldless idea btw.
So, if you still want to do without a shield, at least consider some reinforcement.
My current T-9 build is 500 T of cargo. The only module I have is a 5A prismatic shield, with grade 5 reinforcement, plus two boosters, heavy duty and resistance augmented. Everything else is as lightweight as possible (including the thrusters, I'm not trying to outrun anyone). I get about 20ly jump range, which I think is quite respectable.
I've been interdicted again by pythons and I high-waked, but the shield held.