Batson/Rainshadow are only available as blanks, so you would have to spend about another $150 or so to have it built. The end price would be about what you'll pay for an off-the-shelf XS10MS. Plus, warranty coverage on a custom is limited to replacement of the blank only, so you'd have to pay again (unless the builder gave you a separate warranty on his workmanship) if it broke to have it wrapped. The advantage to having a custom wrapped on a 120 1L as opposed to the store-bought XS10MS is better components, thread colors of your choosing, and placement of the reel seat where it's comfortable for you instead of comfortable for Joe Average.
Rainshadow has 10' blanks too, but IMO they're too fast a taper to make a good all-around rod. Try working a pencil popper with a fast taper rod, then do it again on a Lami 120 1L and you'll see the difference. And, moreover, feel it in yer forearms.