Yeah, lots of backfill now about what could be floating around in secondline and garrison clusters . . . but you have to take into account the Jag's pride. I was planning to weed out the Commandos and consider the PPC armed Firestarters to really be Panthers but I think the Dracs would have been more likely to lose Dragons than Centurions just b/c of their make up.
Proud Jaguar warriors would take Clan equipment over IS any day, and they did by the books which is why it was a flap about the Huntress garrison- it wounded Osis pride. As a Clan warrior I would much rather have a Locust IIC 3 or Incubus 1/2 over a AS7-D or -K. Or even a Howler from trade with the Falcons.
Though I had forgotten about the C refits as a option. Lots of good choices for the secondline forces to offer variety and challenge.
Its up to you, after all its your scenario. I am just saying that I would not be surprised if there was a large amount of IS machines being fielded by the Jags during this time. I don't think that solahma troopers would shun the inner sphere mechs as much as you think, especially if refitted with clan tech. Think about someone like Ter Roshak in the Jade Pheonix trilogy. This was a Falconer Commander, maybe not the most prestigious rank, but they sent him out to die with an assault rifle, and he gladly took it into battle. I don't think that these extreme backwater solahma units are going to object to an Inner Sphere mech instead of a assault rifle.
I think that C refits are your friend, homebrew ones would be easy too, just swap inner sphere equipment for clan stuff like MBear said.
I would also look at subbing in some more Smoke Jaguar specific mechs, here are some I would specifically look at adding in to the game. All should be common Jag machines and fill a niche or roll of an IS mech or clan mech in the OG game.
Arctic Cheetah Firestarter / Raven / Uller / Cougar
Mist Lynx Firestarter / Raven / Uller / Cougar
Great Wyrm Centurion / Hunchback / Hollander II
Ebon Jaguar Loki / Thor / Mad Dog / Jagermech
Horned Owl Firestarter (especially the W)
Stormcrow Hunchback / Catapult / Jagermech
Dire Wolf Atlas / Masakari / Awesome
I would drop all of the Hollander II's and replace them straight across with the Gauss Kit Fox (A I believe).
What you have to be really careful about is adding too many clan machines to the mix, especially at the beginning. In mechcommander the results weren't as skewed, and oftentimes by a couple missions in my forces were equipped primarily with clan tech. On table top, a single clan light is going to wreck your lighter units, Firestarters, Commandos, etc. So it will be important to ration the amount of clan machines you inject into the scenarios. Either that, or allow for a larger mercenary force of your own mechs to go up against them. I'm not saying to make it a cakewalk, but the scenarios are going to be challenging as it is.