If you give the Shadowcat that boost of speed, it'll go as fast as the Uziel, carry more weaponry than the Hollander, and out-brawl the Bushwacker, all while running Clan cool and having the profile and maneuver characteristics of a Light 'mech at a price that every player will be able to afford at some point during a game? There would be literally no reason to ever take anything else in the Medium category. Maybe the Heavy, too. Please, no. Don't let more perfectly good 'Mechs be even further outshone by the work of wonder that is the Shadowcat*. It doesn't need the help. The beast is good enough, just the way it is.
* With the exception of the Shadowcat E, which is poop-balls. This, of course, is only in comparison to the other Shadowcat variants, all of which are excellent. Compared to anything else, the Shadowcat E is still a Shadowcat, and therefore, superior in every way that matters.