I have a similar setup. You are going to like it a lot.
As far as I can see, all of your proposals are fine. Here are a few suggestions, though:
1) I would recommend installing a master shut-off switch for the DC (if you don't already have one). It is good to be able to easily shut down all DC loads. The path from the battery to the inverter should go through this switch. However, the line to the second alternator should NOT, else you risk somebody switching it off with the engine running, which would damage the alternator due to loss of battery load reference.
I used the Bluesea 7701:
2) After you disconnect the ignition wire from the battery isolator, replace it with a push-button switch on the dash. That way, you can use it as a "boost" relay in case your chassis battery is ever low.
3) If you have solar or if you store your vehicle plugged in, consider adding a Trik-L-Start across the relay, to automatically keep your chassis battery charged. Don't wire it through the main switch. That way, you can power-down for storage and still get the battery maintenance.
4) Make sure everything is properly fused. I really like MRBF type fuses mounted directly to the battery terminals:
Whether or not to put a fuse on the alternator side of your 4/0 wire is controversial. On the one hand, it is a current source. On the other hand, if it blows it will damage the alternator (see #1 above). I compromised: I bought the fuse but never installed it.
5) There is an LED output (two, actually) from the Balmar regulator that you can use for status monitoring. I ran a wire from it to an LED mounted on the dash. You can watch your regulator throttle down when it gets hot. Unfortunately, there are a lot of things that turn on the light, so it is of limited value.
Hope this helps a little. Let us know how it goes.