Is the "0-24 dives" in your profile accurate? Because if it is, I would caution against building a handled rig for swimming with sharks when you're at <25 dives - if nothing else, it will be highly frustrating as your attention is split between keeping buoyancy, maintaining proper breathing, keeping track of the reef and other divers, and the large camera on top of that. An action camera such as a GoPro, on a small handle or a telescoping stick is really the best choice for a beginner - and as you feel more comfortable in the water, you can put it on a handled tray, add a light or two, and improve your results significantly.
The Olympus TG-6 is a great macro camera, especially when paired with small strobes such as Inon S-2000, but the wide-angle capabilities of such a setup are somewhat lacking - and shooting large, fast-moving sharks is a scenario that plays to TG-6's weaknesses rather than its strengths.
Sony A6100 (the replacement of A6000) is a great camera, but consider the cost. Body alone will cost you $750, 10-18mm wide-angle lens $900, pair of Inon Z-330 strobes with ball mounts and batteries about $1400, tray with arms and clamps ~$300-500, SeaFrogs housing with 6" dome $500, vacuum system $120, miscellaneous accessories (memory card, spare batteries, chargers, lanyards, etc), at least another $100-200 - you're looking at over $4k in initial expenditure, plus somewhere in the neighborhood of 10kg of packed weight. If you want to add macro capability to such a setup, you'll need to spend $550 on a Sony 50mm macro lens or $1100 on a Sony 90mm G macro lens, plus another hundred for a port, plus floats to get the rig neutral, plus possibly another $300-500 on a close-up lens for supermacro. If you want a nicer housing than SeaFrogs (I use one and I'm happy with it, but tastes vary), a Fantasea will be in $2-3k range with ports, and Nauticam will easily push $5k+ by itself if you go with a glass dome.
An additional point to consider is that if you dive with a large rig, your entire dive is all about the camera - it is pretty much the center of your attention. Whereas with an action camera, you can hang it off your wrist, or clip to a BCD D-ring, or stuff into a pocket, then retrieve if you see something interesting, a handled rig with a large dome and strobes will not give you such options. While you're diving, the way you perceive the environment is through a mental filter of photo opportunities - not necessarily a bad thing, mind you, but something to keep in mind if as you're considering making the commitment. You will also need to spend an appreciable amount of surface time, before and after the dive, taking care of the camera rig, and your luggage - particularly if you're also hauling your own dive gear - just balloons. I came back from a three week trip to the Philippines last week, and a I had a 32kg checked bag plus a 15kg carry-on.
