Emergency generator??

I would think that running it like you say as a nighttime generator and on a load would be good for it.
I am not an expert by any means, but

Worse thing is for it to sit un-used not running at all and hoping it will run fine when needed in an emergency. It is also good for the generators to be ran under a load, if it were mine I would absolutely run it and power on what it can run.

I have no idea WHY Lazarra set it up that way and was puzzled at some of the things it didn't power, I think fresh water pump was one of them. I'd convert it so you can choose to run whatever you want on it, as it's oversized for the little stuff it did actually run and no reason to put any hours on it except in an emergency

Why, isn't that 24V DC?

Ask Lazarra, but the way they did the backup generator is incredibly stupid. You would never run it (not even as a night time generator) because it won't even power the things necessary to live on the boat even with the HVAC off. It only will power 1 panel out of 4 electrical panels in the boat and only certain items are on there and those are the ONLY things you can access with the little generator running. The little generator at 13.5 kw is oversized for just that panel. If you could send the power to the main electrical panel where the other gen power is accessed you could run a few ac's off of it, or whatever you want and more items. I had an owner that was highly interested in a 68' we looked at a few and even sea trial/surveyed one of them, which is how I came across this weird generator situation.

If the two genset are close enough each other, it might be easier/quicker to parallel the two outputs with a 3-ways disconnector in between, for putting either one or the other on line as desired, but never both.
This way, you wouldn't need to fiddle with the electrical panel, which could be left on Line 1 at all times.
Of course, you should "self-limit" the loads when you're running on the smaller genset, but that would be true even with a more sophisticated integration.

It's set up that way for regulatory compliance, as certain 'vital' loads are required to have two independent power sources.

The genset provides 240 Vac to port+stbd blowers, fresh water pump and emergency bilge pump. It provides 120 Vac to engine room lights, battery charger #1 and galley panel emergency loads which are detailed on sheet 3 (not shown).

The down side to rewiring in order to power anything in the panel is that it's then possible to overload this genset such that it is not available for vital loads when required. It is not as oversized as it might appear and must be sized to run all connected loads simultaneously.

Nice quote CR.
You must never remove the interlock. Multiple AC sources cannot act in parallel without aligning phases, not an easy or cheap thing to do. For vessels of this size and complexity ensuring that only one source can energize the panel at any given time is non-negotiable.