Yes 50/50 split House bank has been proven as wasteful, too much dead lead, see Peukert effect.
But I like the idea of eliminating all batts other than the main House bank, then creating a Reserve composed of the same batts, sized large enough to carry essential loads, safety
Cranking can be usually done from House, but switched over to Reserve often enough to confirm all is well there.
Belt & suspenders cranking backup is a portable lithium powerpack.
To really take advantage of Peukert, House and Reserve can be combined by an adjustable high-capacity LVD, like a VSR but with a low enough setpoint that Reserve only gets isolated in exceptional circumstances, SoC gets lower than usual, say at 60-70%.
No actual dead lead, maximum bank life so lowest cost $ / AH / year, plus decent redundancy.
Yes unconventional but I would argue no less KISS than most large & robust House setups.