No disdain for craft here! If you were referring to me...
I'm not interested in fighting someone. My advice comes down to this: find a tool that you love using and use it. At the end of the day, the most important thing is that you make stuff. A tool that helps and encourages you to do that (rather than making you dread the process) is very helpful and definitely a step in the right direction, if you can afford to get one. Some people do amazing work on a T2i (looking at you Kendy Ty), but for some people, the limitations of that camera (and every camera has limitations) make a creative block. You, Sharad, came on this forum because you're experiencing a creative block that you feel is at least partly due to the limitations of your equipment. Who am I to tell you you're wrong? From what it sounds like, a C100 is a great upgrade, and I believe it will help you do some awesome stuff. It's definitely a camera that HELPS make things--very easy to use with great results (though you will still have to know what you're doing to make the best of it).
Those are my 2 cents. Hope they're helpful Sharad!
Any time. Unfortunately you're entering a world where people are waiting to tell you you're "doing it wrong." I'm more of an advocate for letting people find their own path. If a new camera is part of the path they want and it's not hurting anyone, then get a new camera!
Pay Lofar no mind. He's more interested in being a pedant than being helpful.
DSLR's are really not designed for quality video images. The T4i is extremely limited, and I don't blame anyone for wanting out of that game. If you can afford something better, why not? I never understood the whole, "Master your own camera first" mentality when it came to tools not designed for video.
It's like a chef telling a student, "master that dull knife before you upgrade to a sharp one." Sure, maybe the dull knife can cut if you try hard enough, but why waste the time?
Used C100 for sure.
Of the cameras on your list, I would also recommend either an A7s or a C100.
I used to own an A7s (with Tilta cage and XLR adapter). It's an amazing little camera. You can definitely get some cinematic images out of it. If you shoot in S-Log, you do indeed capture about 14 stops of DR, but you have to crush the darkest parts of the image due to noise; so I would say you come out with about 12+ stops of DR with a nice curve and good highlights. BUT, shooting in S-Log can be a major pain because of the base 3200 ISO. Also, you're scraping the bottom of the barrel when you try to color that 8-bit footage that's been stretched so thin.
The low light is indeed amazing, but don't expect to go over 12,800 ISO.
The EVF on the camera is fantastic! I never felt like I needed a monitor to judge anything by. The EVF image felt very true to life.
You can shoot up to 60p in full resolution, and 120fps at 720p. That's fun.
The worst part of the camera is simply the handling. The record button is in a terrible position. I didn't think much of it when I bought it, but after a while it really starts to grind on you. The camera is just SUPER light, which makes it hard to keep steady under most conditions--you'll definitely want a rig. Also, it's neat that you can adapter almost any lens to the camera, but sometimes I just don't like using adapters.
I work with the C100 very often. I love that camera. It's extremely easy to use. You really don't need any peripheral accessories except perhaps a better monitor and your standard tripod/should rig, etc. The camera itself, though, is just ready to shoot.
Honestly the ONLY drawbacks with the C100 Mk I are the crummy EVF (it really is almost unusable), and the lack of high-speed options. Not being able to do 60p is a real bummer. That's why I plan to get a Mk II, when I finally get one of these cameras.
The dynamic range isn't as good as the A7s. I would say you're missing about 1 1/2 stops in the end. That means you have to be more careful with your exposure or you'll clip those highlights, and it won't look cinematic. BUT, if you know what you're doing and know how to treat the footage in post, it can look great. Maybe the A7s has a slight edge on the "cinematic" side of things, but it's not much, and I would absolutely trade that edge for the ease of use the C100 offers.
TL;DR. If you don't need slow motion, get the C100. It's a pleasure to use and creates images about on par with the A7s. If you do need slow motion, the A7s is a great option too.