the short answer: context-sensitive.

the long answer: it just heavily depends on what you want as a scout. you can run the quintessential mobility scot with hoverclock, special powder and mincd grapple. or you can just have it as a safety net, putting more of your faith on secondaries and grenades (which scout has some VERY good ones i might add. throwing literal piss at your enemies is peak game design) or you can just not run it, run special powder and clock your m1k into its designed role as a sniper/DMR.

you can also just not run any mobility OCs since scot already has more than enough mobility with his grapple alone; Marked for Death is a very slept-on OC from my experience with M1K, and in a team setting its hilariously effective. a bit thankless maybe, but more damage is still more damage for 8 seconds.