Considering scouts make up roughly 1/10 of space marine chapters they really should be there in some form. And as every space marine to ever exist has been a scout at some point... I just assumed it would be like the tutorial class or something. Start as a scout with a bolter and then branch out into Tactical/Assault/Devastator or specialist role like Apothecary/Librarian/Techmarine.
I am betting that the Tac marine will have wargear options to represent a scout. Easy enough to do but as I'm not seeing a lot of RPG here it wouldn't make sense to start you off as a scout. Maybe a Tac with scout wargear.
