It doesn't take anything like 30 gallons of dilution water on the local end to avoid the slug of cold/tepid water from dropping the output temp of the local water heater to below showering temperatures. With 3/4" plumbing you're only talking a couple of gallons of water, with half-inch it's about a gallon. You could probably do just fine with a 10-gallon heater on the MB end when plumbing them in series. But since you have the 30 gallon version and the space, go for it!
With short-draws for hand washing etc the hot water from the gas heater never arrives, and that heat is abandoned in the line, and quite a bit of the water heating will be electric, but during bath or shower draws it will be substantially from the gas heater. By getting rid of the recirc you'll be abandoning LESS hot water in the pipes than with the local tank though.
Insulating the hot water feed from the gas-fired tank means you'll be losing less to the crawlspace, for a higher-fraction of gas heated water overall. Don't cheap-out with the crummy R2 goods (3/8" wall) found at box stores- go with R4 or better 5/8" or 3/4" wall stuff, even if you have to seek it out. Plumbing supply houses may carry it, but if not the local supply house, Graingers or internet stores sell it. Some TrueValue Hardware stores carry the fat stuff for half-inch plumbing, but not for the 3/4" plumbing. Given you have 90' of distribution plumbing in crawlspace it will pay to get the better stuff.