You're just repeating that they're great, but AC-5s are also 3025 tech and are better. And even AC-5s are very niche when the only useful specialty ammo is flak. Unless you're AA you should have been using energy weapons or missiles. If you're AA the range of the full size AC-2 was actually valuable because there are VTOLs that can fire from outside LAC-2 range, but not full size AC-2 range.
There is no benefit to a low heat option if it's heavier than a high heat option and enough heatsinks to make up the difference. Two LAC-2, two SHS, and a ton of ammo come to 11 tons. Two LRM-5s, four SHS, two tons of ammo, and a medium laser also come to 11 tons. The latter is just better unless you're so packed with endosteel and ferro-fibrous armor you can't find the crits. In 3025 that's not an issue.
Again, why aren't you using an AC-5? If you're using rapid fire rules they apply to it too. It can use flak or precision ammo just as well.
First off, I would never put in 2t of ammo for 2 AC/2 in 3025 and not for 2 AC/2 or LAC/2 in 3050+ -a single ton will do, I doubt what I was suggesting in a 30-40t design would last 22 or 11 rounds of fire (supposing Prec for 3050+)- of course I would also not give 2 LRM5s a second ton of ammo either for most conditions. I am not sure why you are comparing the 2 LRM5s and a ML to the 2 LAC/2 that are heat neutral since the LRM set would not be . . . but its also not like it matters on most 3025 40t and under designs, rarely do they need more sinks. IMO, four things your LRM scenario is overlooking . . . the LACs will not have the minimum range problems the LRMs will have- in fact, their short range is where the LRMs start adding to their numbers.
Also, either 1 ton of ammo or your 2, the LACs will have nearly double the battlefield endurance. Might be too much but honestly a pair of LAC/2s are going to be 'fire every turn, so what its a 12.'
Third you do get a couple of scenario situations where missiles are messed up but ACs are not.
Finally, 'LRM5s are superior for everything at range, MLs are up close' exploits some known situations (3 LRM5s weight less than a LRM15) and is boring. If you want to spam LRM5s, be my guest but you were asking about situations were a LAC/2 could make some sense so . . .
Take a hypothetical 3025 variant someone suggested, the Clint 2-3T . . . swap that AC/5 for a LAC/2 and you have cut the weight of the gun down by 4t. Which is a LOT you could add to that design . . . you could max the armor (52% sq), add a few heat sinks so it could jump and alpha w/ 1t for armor, you could replace the CT ML with a Large Laser if you wanted to, or quite a few other possibilities. But now that fast low weight medium has a bit more to it while keeping a ranged plink'ing harasser.
For a 3050 option . . . no longer does it really work on a light mech with the introduction of DHS, just too easy to put a ERLL like the Spider or a ERPPC like a Razorback. To me it becomes a cheap ranged vehicle/speedster hunter . . . you can take a bog standard 3025 Scimitar, pull the AC/5 and put 2 LAC/5 with a single ton of ammo and get slightly more salvos- 11 if using precision. Move about the battlefield and plink at the heavy/assault armor or damaged mechs for relatively low BV, precision just allows it to hunt its counterparts better.
AW- nearest point in the flight path
