So, after a bit of research, I found 2 lithium batteries that are designed and guaranteed for used for cranking, and work directly from the alternator.

12 Volt Lithium Cranking Batteries | Buy Online– iTechworld - however they told me it wasn't really designed for auxiliary use. Therefore, an extra battery and DC-DC charger would be required. Still might be a decent option to replace my cranking battery, and may work out cheaper than lead acid in the long run.

12V 80Ah Extreme battery (LITHIUM) - not the cheapest, but apparently would work for both.

I think this device Victron Smart Battery Protect SBP-100 will work ok to protect the cranking from over-discharge and allow for starting the vehicle.

I still need to consider total cost of ownership, which isn't a clear choice for me yet...