Yes, you can just replace the top brake line. Whether or not removing that brake line clamp will work for the stock line in your situation depends on the exact adjustment of the risers, as well as the adjustment (rotation) of the bars in the risers. Also, how comfortable you are with a snug brake line.
I got the extended brake line, thinking it would be a snap with the wheel and forks off, but getting to that fitting above the radiator is a real witch. (The fitting is threaded into the back of that block and there is NO slack to pull it out. Also, there is a little tiny brass "olive" that has to go in there before you tighten it up.) You need to remove the radiator for access, and to do that, it looks like you have remove a bunch of plastic, and maybe drain the cooling system and remove hoses? I was running out of time (was doing fork springs and engine oil change) so I decided it wasn't worth it. I found an adjustment of the Rox risers and the bars that feels good for me and works with the stock brake line. Gets a little snug at full left lock, but I just try to avoid that most of the time (mainly when parking). I may make a little extension bracket to bridge that lower clamp to the mounting bolt to keep the line in place when turning the wheel.
2014 V-Strom 1000 - Desert Khaki
2011 Burgman 400
2007 Honda Helix
2013 V-Strom 650 - sold