It seems like a lot of money to make a little more power. The .560 cams are only slightly more aggressive than the stock Buell cams. I'm pretty sure the 1275 kit yields the same CR as the Buell setup. Maybe .25 more? I didn't see any mention of headwork, which may negate the potential increases in power also. I'd at least go for their Impact headwork.
Its not like you're converting an 883 Sportster to 1275 and looking to pick up a LOT of power for that same amount of money, as most of the Buell stuff is pretty "high performance" already.
As far as remapping, what do you have in mind? Its not like you can just plug in a PV for a Sportster and start making changes or drop in a Sportster map. I'm not saying it can't be done, but finding someone who can actually do it (and do it right) maybe a lot harder than you think.
You may want to run this by the crew at Hammer. Aaron, Dan and the crew have done a lot of testing of various 1275 setup and it won't be their first rodeo with an XB either. They have detailed several packages (by HP) with what parts are recommended to make XX HP, along with a cost breakdown. It sounds like you are looking at something along the lines of their 90+hp kit. I think stock XB's made about 85-90hp on the dyno, and closer to 90hp with a Drummer. There is an "exhaust shoot out" article written up from year ago, and while most of the exhaust manufacturers are long gone, Drummer, Dean Adams and a small handful of others still remain. Kevin at Drummer (KDFab) is awesome to work with and does great work. The stock Buell muffler works great as it is, but it also had to work out EPA regulations and other restrictions to be legal on the bikes, whereas everyone elses are "legal for non-highway use".
I'm not saying your idea wont make more power, but is it going to be worth the money?
The stock crank should be OK, and the 08-up crank would be a better choice, but they are basically unobtanium anymore. You could also send out your stock crank to Darkhorse or another shop for rebuilding/lightening/balancing, but that will really blow the budget out of the water. And if you're going to go through that much trouble and split the cases, you may as well look into the 90" kits. And remember, before the 2008-up crank was introduced, all the HP stuff was done to the 1.25" crankpin cranks without a second thought.
Our forum bad-ass Mike Lowary did something very similar, and the end result was legendary. It was not cheap, it was not expensive. It was outrageously expensive. Is it worth it to you?