Was thinking of Warhorn, but that renders some traits pointless while active.
What I consider the main advantage of Furious Speed in this build is simply that it's a convenient way to maintain swiftness yourself, without being dependant on outside sources or being "stuck" in a weapon-set that renders key-traits for the build obsolete for the time being.
Losing Furious Speed as such isn't a big deal, however, the trait allocation doesn't make all that much sense anymore if you swap to GS often during combat. In that case, I would let go of the strength-traits as well as dual-wield-agility and put these 3 points into discipline instead for fast-hands.
Lastly, if you like playing GS in general, maybe the GS-variant is better suited for you? It does however provide less vulnerability, depending on your group compositions, that may or may not be an issue.