Interesting read. Thanks. I can see both sides of that argument. If you typically walk away from your boat with everything turned off (re. the switch and shore power), I think wiring the Echo on the downsteam side of the switch makes more sense. If you typically leave a charging source on when you walk away from your boat, it makes more sense to wire the Echo directly to the batteries.
My current configuration uses a relay style combiner. It has always worked well keeping both banks charged and I get 5 to 6 years out of all the batteries (alot considering the wicked heat down here in the Galveston/Houston area). However, those Gel batteries keep going up in price and I have to use Gels for both house and start. I'm trying to modify my configuration so that I can use a small Auto Start battery and either Gels or AGMs for the house (perhaps 6V next time around). I want to do this slowly though as the cost of upgrading everything would be substantial. My House Gel is now dead and my start Gel has another couple years to go. So, my plan is to move the Start Gel to the house, by a cheap auto start battery, and an Echo. That will save me $100 now. I know that isn't ideal because of the Gel charging parameters but the Echo has enough voltage drop that I don't think it will harm the cheapo start battery. When the other Gel dies, I'll replace it with an AGM (or 2 6V AGM Cart batteries).
With the new configuration using the Echo, when I walk away from my boat with the switch off and the shore power cable disconnected from the dock (99% case), the Echo will not slowly bleed my house battery.
In the rare case that I'm away a long time, I leave the switch in the on position and connect a solar maintainer to a CigLighter plug wired to the panel. This way, the house battery gets charged if the event that the Bilge pump runs a bunch for some reason...