Re Hanse & their importer in Australia. I think you may need to translate the Scotty AI stuff to get them to engage. What you are proposing is not that unusual. In essence you want to run a 48v LiFePO4 battery bank alongside a high-power alternator. An alternator controller manages the alternator load by measuring load, temp, volts etc.  Not unusual except for the voltage. That controller works together with a high current (3Kw+) DC-DC buck boost converter to charge the batteries at 48v while alternator is supplying loads at 12v. Alternatively, if the alternator is not supplying power then the DC-DC Buck Boost converter provides 12v from the battery bank. Bi-directional DC-DC conversion is relatively unusual with step up/down in voltage so that will be new to them I suspect. I’ll bet you’ll get some further conversation around failure modes but I won’t dive into that now. 

In dealer speak you need to delete the standard batteries and supply your own. Likewise you may need to delete battery combiner elements from the order, which may impact on DC switch panels etc. Engine should arrive with a standard alternator which you either swap out for the high power one or fit the necessary extra mount & belts solution to have 2 alternators (if you are going to these kind of costs that makes some sense. You might even want to run one at 12v and the other at 24v).  

Running loads at a different voltage to the batteries is what’s confusing I guess but this is not new. The idea has a great heritage in fact!  Look up boat maintenance guru Nigel Calder’s Integral boat power system which supplies 9Kw :) It’s even linked by Victron themselves in their blog -  see https://www.victronenergy.com/blog/2018/10/03/nigel-calder-and-the-integrel-9kw-alternator-on-steroids/