No, the variants have their identities from the tabletop. That's where they came from.
A CN9-A is a Centurion that doesn't mount an AC20. There's nothing that says it can't be customized to mount an AC20.
And hardpoints have never been a thing. If they were, we wouldn't have "Swaybacks" with six MLs in place of an AC20. Or a Catapult with twin PPCs in place of LRM15s.
I feel like I'm taking crazy pills.
Its your interpretation on hardpoints; specifically the ballistic/beam/missile type and not size. (Mechwarrior4?)
Swayback (6 ML) - the medium lasers are all mounted in the RT previously reserved for the AC20. Is that not the same as a hardpoint?
Other variants have various weapons mounted in the RT
No weapons SHOULD be mountable in the left torso or center torso of the Hunchback.
(In which case I disagree with the SP variant which mounts a SRM6 on the LT being the exception to this rule)
Catapult with twin PPCs are mounted in the arms to replace the LRMs
No large weapons SHOULD be mountable in the RT/LT of the Catapult
Want 4 Large lasers? All 4 go straight to the arms. (None allowed in the torso)
etc
I maybe downvoted for this but Mechwarrior4 was on the right track for weapons mounted by size.
Classify the weapons by size and where you can mount them. (criticals in TT do a poor correlation because of heatsink/ammo allocation of weapons)
In regards to the Centurion, yup the AC20 should be mountable in the RA to replace the AC10
But it should also be reasonable that you can't just mount just one single AC2, medium laser or machinegun in the right arm. (unless its damaged)