The TG's strong suit is definitely macro. For wide angle, manual control, and faster midrange focusing, the bigger cameras will likely give you better images after you dial yourself in. What are you using for lighting? Focus and enough definition to crop images definitely depends as much on good lighting as on steady hands, and lots of TG users find wide-angle comfort in the wide wet lenses. I expect you could find a rental rig on one of the camera sites (Backscatter, Bluewater, others) for some testing, although the learning curve is steep. I really like Martin Edge's book, The Underwater Photographer, which includes the spectrum of equipment from compact to DSLR; if you haven't read it, or something like it, it might be a good precursor to an investment decision.
The EM-10/IV kits from Backscatter range from $3300 to $4300, with the camera and some glass but without a tray, arms, clamps, strobes (don't let anyone tell you one is enough for wide-angle) and cables, a way to trigger the strobes, a focus light (and possibly a video light), an extra battery or two, maybe an external charger, a way to carry it all . . . so you're pretty quickly at $5-7k, assuming you're ok with Backscatter's proprietary housing (which I assume is of good quality--they're a good company). The 10/IV has the same sensor as the "former flagships" M1/II and M3/III, and has five-axis IBIS, which is great, mostly for topside use. And everything would be under warranty, of course.
Could you find a used but in great shape E-M1/II or /III for significantly less? A good place to get a feel for the used market is the Classified forums here and/or on Wetpixel, where a Nauticam M1/II housing recently sold for $1,000. Used bodies rated EX are around $600-700 on KEH. If you could find good used strobes, they'd still be $700-1100 for a pair. A couple of lenses, a couple of ports . . . I think you're at about the same place, said and done.
I did a few hundred dives with an OM-1 Mark II system, and it made me happy. A lot of folks are still using them and will be for awhile, but they'll trickle onto the used market. But I don't think you'd save much, or see a ton of benefit, by trying to put together a used kit rather than going with the M10/IV.
Happy shooting!