Kerensky used the Orion, and for good reason. The mech mounted more armor than any heavy mech in existence, just about, and more than most assault mechs. It had diverse weaponry: LRM-15, Autocannon-10, SRM-4, and 2 Medium Lasers. It's only flaw was too much ammunition reliance and not enough heat sinks. Once it's 16 salvos of LRMs and 20 rounds of Autocannon ammo were expended it had a tough time coming to grip with the enemy, though it had enough armor to safely disengage.
With the rediscovery of star league technology the mech could easily be refitted to have an LB10X Autocannon and ferro-fibrous armor which would free up enough weight to install CASE around it's heavy ammunition loads and put an Artemis IV FCS on the missile systems. Cost effective double heat sinks would enable it to really tear up enemy mechs at the 180 meter range sweet spot.
At least, that's what I would have done, but, instead, the designers for House Marik decided to gimp one of the toughest mechs on the battlefield by putting an XL engine in it.
Just say "NO" to XL engines.