Give him a Lum Berry and put the last 4 EVs in defence so you have an odd HP count and that is the definitive Garchomp lead, yes! That's an option. One thing that would mean though is you can't use Exca effectively due to lack of Sand Rush boost (before you ask, don't use Scarf, it's not a good set since being Choice locked into Rapid Spin kills your momentum completely). That's not really too bad a thing since your team isn't really weak to hazards at all so spin support isn't vital, I'm just making a point.You say Garchomp isn't viable today except for SD+SR or Choice Scarf and I was thinking about putting Tyranitar specially for using SR.
What if I use Garchomp as a lead like this:
Nature: Jolly
EVs: 252 Atk, 252 Spe, 4HP
Ability: Rough Skin
Item: Rocky Helmet
Movestet:
Dragon Claw
Earthquake
Swords Dance
Stealth Rock
This would be instead as Stealth Rock Tyranitar, it would also leave a space open in my team, what do you think?
Tl;dr, yup that's the lead Chomp set more or less, but now you can't use Exca effectively so replacing him is advised.