Re Smart External Regulators
There are a lot of them on the market and they mostly work the same way, except the Sterling units which don't require alternator modification (I don;t understand how they work). The majority require you to modify the alternator to disconnect the internal regulator and bring out the wires from the brushes (the field connection) to connect to the external regulator. That's easy enough to do, but you need to be aware that the standard Leece Neville 175A alternator is not continuously rated for full output. In other words with a smart regulator and low SOC batteries, when you start the engine, the reg will deliver max field current to the alternator and it will produce 175A - until either the batteries charge up quickly and the current drops or the alternator burns up. You need to be aware of this so that you can manage the system, by either not allowing the batteries to get too low (always a good plan) or being prepared to start the genset and switch on the battery chargers to relieve the load on the alternator.
There is information in the FILES section on alternator mods for smart regulators.
Another useful thing to have is a switch to disconnect the reg field connection when your batteries are fully charged so that when you are running the engine for short trips around the marina, for example, you don't start up a charging cycle when you don't need it.
I don't know anything about heaters !