I now have a little more than one year on my 36’er after about 4 decades on a 24. I have become more than a little frustrated with the massive wheel weight, particularly during a long out-of-the-saddle climb that I did last weekend.
Anyhow, I’ve been casting about online for who has done what to improve on the rotational weight of this wheel and came across Saskatchewanian’s very admirable sewn and bonded custom 36" Racing Ralph tire on another thread, which led me back to my bicycle racing roots, which included the necessity of having a needle and thread handy for tube repair. The beauty of tubular tires is when they handbuild a casing, they cut and glue it to whichever length the application requires, cut and glue a latex (super-light) tube to the same length, and sew the casing around the tube!
And the weight!?! The widest Cyclocross tubulars weight around 400g.
And my search for any discussion that connects unicyclists with tubular tires, landed me on this three-year old thread, which seems to have an abrupt termination, but a very enticing idea. Did you ever manage to get anywhere with the tubular maker on this project Unisk8r?
Either way, it’s clear that the tire is the primary answer to the weight problem. if I assume that a tubular tire can be acquired (and it wouldn’t be too difficult), the challenge would be the rim. Not such a large challenge, as the perfect tubular rim would be any rim of sufficient axial and lateral strength that has a smooth semi-circular surface to glue the tire onto. Isn’t this EXACTLY the type of rim already in use with non-pneumatic tires on both modern high-wheelers and over-36" unicycles!!! 
The rimstock for those wheels shouldn’t be so hard to acquire for a 36" application.
For that matter, I have seen John Foss comment before that the primary problem with 36+ is the lack of pneumatic tire. Tubular tires may well be worth chasing down for that application also!
I hope that unisk8r can bring the tubular tire maker that he was working with back into the loop, but either way, let’s get this discussion fired up again!!