I'd actually bet on it being a Hyper Velocity AC, it is Capellan after all and they do like HVACs.
HVAC, Stealth Armour MML9+ Artemis, Guardian or Angel suite on a Medium or a light you're not going to get much more on.
Given the name I'd wager the
Calliope is Canopian, though as the two nations are now joined at the
hip womb I admit there is little reason to quibble about the 'Mech's origin. That said: Great Cat please don't let that be an HVAC of any variety! #P
If it is some kind of long range design (LGR or HVAC) then stealth armor would be rather nice, though it may be worth noting that Artemis IV would be useless with that kind of heat profile as there would never be a reason to disengage the stealth armor. [EDIT: Could one use Angel ECM for both stealth armor and for ECCM to allow ArtIV to function? That would be rather neat] More than likely we don't have long to wait to find out though.
My current (completely uninformed and useless) speculation: Either a MAF trooper with a plasma rifle, MML-9 combo or a medium stealth sniper with a LGR and MML-9.