24' yurt on a concrete pad? hydronic heat?

[turbotoyz]

Hello -- first post here but I've been reading a lot.

Getting ready to order our new yurt in the next couple of days. A few questions regarding my planned buildout:

I'd love to have someone shoot some holes in my plans or offer suggestions about what I may not be thinking of.

I want to pour a 30' by 30' concrete pad 4" thick and build my yurt on this platform.

Specifics:
* base -- 2 inches of compacted 5/8" minus gravel, which is on 3 inches of compacted 1 1/4" minus gravel
* 6 mi vapor barrier
* 25 psi dupont style insulating foam board
* 4" concrete pour on foam board (not looking for big discussion about this part; read lots about it on concrete forums and pours on foam board are awesome)
* pour will have lots of grid based rebar
* pour will have control joints to mitigate any settlement (there should be extremely little, however)
* pad will be protected by excellent drainage

I want to plumb PEX for hydronic radiant heat in the 24' diameter part of the pad where the yurt will live.

Questions...
* generally... is this a bad idea? why?

Has anybody done this? It seems like it should be excellent..durable, sturdy, and the concrete is an excellent conductor and thermal mass for the hydronic heat source.

What is the problem here? I know I'll need to factor in how to tie down the yurt...but what's wrong with this approach?

Thanks everyone! I'll post pictures as I'm building out over the summer. I got lots of fun stuff going on out on my land.

Edit: buildout site is about 30 miles east of Seattle...rainy but not particularly cold. expect maybe a week max in the 10-15 degree F during winter.