The Passport also doesn't play well with normal rechargeable (Li-Ion) cells, since these start at 1.3V and from my testing that's approximately where Passport stops working due to too low voltage.
Did you mean NiMh cells here? Li-ion produces 3.7V. Or am I missing something else?
They explicitly recommend Lithium cells ~ they are very uncommon and expensive. The ones that came with my Passport lasted for probably 4h; while Alkalines last maybe 15 minutes or 30 tops.
I didn't even know Lithium AAA batteries exist. I think a better solution would have been if the device fits 3 batteries. With some voltage regulation, anything between 3.6 and 4.5V can be brought down to 3V, so that standard AAA batteries can be used until it's completely drained. From your pictures it looks like that would mean a slightly wider device.
4x rechargeable constant voltage (builtin charger): 25€
I didn't know these exist! It looks like a great solution, but won't solve the "10-20 years time" problem.