Experiment time I guess.
2010 DS used trade in value is 2785, Lets round it off to 3k for private sale.
A used 2012 DS ZF6 cost 6000 right now on cycle trader
You claim 23 mile range on your 2010, zero claims a max of 50 but who knows what test they used.
Zero also claims the 2012 ZF6 gets as much as 75 miles at city EPA UDDS or 42 miles with mixed highway / commuting at 70mph.
I will assume your range now is highway / commuting speeds for comparison.
At a cost of $500 you will get a hypothetical range of 32.3 miles (9.2 miles), This doesn't take into account the cost of a doctor to fix your broken back since you will have to be crouching 100% of the time to get this range increase or the time you will spend fixing the cowl to your bike.
Cost effectiveness per mile is $54.35 / mile increase if just looking at the cost of the fairing.
At a cost of around $2000~$3000 you will get a tested range of 42 miles (19+ miles) not requiring you to break your back and no time spent modifying the bike to get the range.
Cost effectiveness per mile is $105.26~$157.89
So basically $50~100 more per mile but I would argue this amount is less given the hidden costs associated with going to a dustbin fairing. I have done a lot of modification to my bikes and can tell you there is always hidden costs involved.
The time you spend modifying the bike,
the money you end up spending on special things you didn't realize you need,
the time spent thinking about how to modify the bike,
stuff breaking after hitting your first serious bump in the road,
in the case of the dustbin fairing having to move your rear set backward to be able to fully crouch,
is the windshield bubble included or is it extra?,
and again the big one for me is my back I am young but I can't ride too long crouched over like that, esp not for 32 miles.
Before making the decision I would try to identify all the above costs and add them into the cost of the fairing then run the numbers again if you think the idea of a 2012DS is something you want.
I won't be one to complain if you take the project on. I love modifying my bikes, it is my hobby to some extent and the cost of doing so doesn't enter the picture if I am enjoying myself doing it. I would like to see your range increase as a result of doing it if you do go this route.