I'm pretty much in the same boat as you John.
My current setup is a FujiFilm X-T3 in a Seafrogs housing. I'm VERY happy with the camera (underrated here imo) as a hybrid setup - 4k 10-bit 420 (422 prores over ninja v) and 24mp images with good autofocus and colours.
Not so impressed with the housing. Don't get me wrong - I think it's amazing for the price and the perfect solution for beginners. But I think my money would have been better spent with a proper housing with full functionality. This one is definitely lacking.
So here's my line of thinking:
Since i'm looking to upgrade to a full housing. I'm wondering if I should just upgrade the camera at the same time to something that is going to be a lot more future-proof than the XT3.
The Zcam E2 S6 is currently at the top of my list and here's why: 1. The NA E2F housing can fit 3 different cameras: the S6, F6 & F8.
That gives me a clear upgrade path if I decide I want to go full frame in either 6k or 8k. With the BMPCC6k (the main alternative) i'm stuck with having to purchase a full upgrade if I want to beef up my resolution in the future.
Not only does this make sense financially, but also means I can offer different options to potential clients. 2. The form factor.
This camera is more along the lines of a proper cinema setup without the big time investment. It's still pricey but you get a lot for the money imo. I hate the BMPCC form factor and the cables all being on the left side. I love the fact that the Zcams are really compact and minimise cables. This is great for me because I shoot a lot topside too.
But mostly I just love the idea of a proper cine camera in the hands compared to a clumsy video DSLR/mirrorless rig when it comes to getting handheld shots. Rigging it up on a tripod/slider might be a bit trickier but I'll cross that bridge when I come to it.
Also the cine-style locking mount seems like a really nice thing to have, more-so for topside but still. 3. A few features on the Zcam compared to the BMPCC6k.
First is the pre-roll feature on the Zcam - This allows me to basically shoot into my buffer and capture a moment AFTER it has happened. The X-T3 also has this feature for stills only and it's been really amazing to have. I can only imagine how useful this would be for video when filming behaviours, especially in fast-moving and shy macro subjects.
Also interchangeable mounts and internal Electronic ND filters. Both of these are great features to have, especially when using certain lenses that won't allow for filters (fish-eye, etc). This gives me a choice of basically any lens ever made whether that's Canon EF, Sony E, MFT, etc (I'm not sure on the full list but I also know there are more coming).
With the Zcam S6 I have the flexibility to choose what resolution and codec I shoot in. This is great if I'm just shooting something for social or mobile platforms, or online platforms such as YouTube that will compress the video anyway. Alternatively I can go all the way up to 6k 75fps max OR even 4k 100fps for certain shots. This is less so the case in the BMPCC6k which is more restricted in that area.
My only hangups, as you've stated, is the ZRAW for editing. I'm of the understanding that it requires proprietary software which is next to useless on Mac, but useable on Windows. That and the need for a monitor, but currently I'm looking at the anglerfish monitors as a non-recording and more streamlined (and affordable) solution.
Bear in mind this is just from my research and only theory at this stage, although I hope to test these cameras out very soon and hopefully that will help me make a decision!
Alternatively I'm just wondering if I should keep the X-T3 for now and get the Nauticam housing for it. Probably won't do that though as I really don't like or trust the side ports for monitors/recorders and power solutions as well as the form factor.