i don't think it's too complex. you have everything you need to accomplish what you want to accomplish (aside from investing in solar). so you're in a good spot.
it sounds like you have 6 batteries total. I would wire up two banks to a simple 1-2-ALL-OFF battery switch. I would wire up the two as bank 1, wire two more as bank 2 and then leave two batteries on the dock or better yet sell them cheap/ give them to someone who needs batteries. it will win you karma points.
Sounds like the regulator on the Beta will maintain things without an issue. Wire up a solar panel or two (with a charge controller) and then you're set. With two big banks, you should have enough to charge the Torqeedo when necessary, off of solar. Keep that thing for the dinghy. More battery capacity is great as it allows you to store more power on a sunny day and save it for a rainy day.
My current set up is a 50 w solar panel on the stern pulpit and an 80 w panel in front of the companionway charging two 105 aH lead/acid's. My boat is engineless, the solar is my only means of charging and it has performed brilliantly between US west coast and Fiji on my 27-footer, just for reference. I use my laptop very much to work remotely, as well as the stereo and 12v fans and a Raymarine ST2000. All lights are LED.
With 130 w of combined solar, I can charge at over 8 amps in ideal tropical conditions with both panels aimed right at the sun, though I usually hover in the 2-5 amp range for charging.