You could charge the under-the-hood 12 v battery via one of these
Orion-Tr Smart DC-DC Charger Isolated - Victron Energy . I am considering this approach to use a (safe) lifepo4 pack to to keep the under-the-hood 12 v at about 14.0 volts. This should offload any accessory electrical use from the Leaf's DC-DC converter to the (safe) lifepo4, adding an estimated 3 miles of range to my 2013 Leafs in nice weather and quite a bit more in cases like yours. Added benefit, the large AGMs I have installed under the hood will frequently get the finishing charge they need for longevity.
As the accessory electrical use gets higher, one will need more ahrs, but you know that.
What we need is good data on how much the DC-DC converter is currently using and under what scenarios. One of the early Leaf docents on this forum stated many years ago that the gauge on the dash showing accessory energy use is bogus, and just reports different usage based on what is turned on rather than an actual current sensor somewhere. I do not know if that is true, but if any one knows where someone has already done this, or the optimal place to add one, love to hear.
Additional details. You will want a 60 amp or larger breaker in two places, a nice enclosure for the auxiliary 12 volts, and a way to charge it conveniently. They make these J1772 to 120 volt adapters which might be a solution, or just a regular inlet somewhere that is convenient.
A lot of work to save a few minutes of charging on the road, but in some cases, like yours, it could make a difference. For me, the idea is to keep the Odyssey AGMs in good condition so that I don't have to worry about their condition. And marginally reduce cycling of the main pack. The main pack s in both of my 2013s are doing well, one above the expected degradation path, and one right on that path.