There's no reason to pull anything to make room for an EO/IR fit, there is more than enough room to fit the equipment into the aft avionics bay. We used to regularly crawl right inside to pull the inverters during maintenance.
I'd go with swappable gun packs, 8x50 for hunting VC, 4x20mm when hunting NVA with heavier equipment/armour. A COIN bird needs endurance, so I would stay with the tiptanks... despite the temptation to fit the rocket pods from earlier Marks. It's going to need a good terrain avoidance radar, what donor bird has a radar that fits? I'm not really that up on birds other than the A-6 from that era, nothing comes to mind. Would the A-6 radar fit the Clunk nose?