I finished the campaign yesterday, after playing the game for about a week. The game is fun, but the fun mostly plateaued around the middle of the campaign (up to Nautilus Castle). What happened was I was worried that the default difficulty would be too easy, so I set it to harder enemy spawns at the start. This sort of backfired, because I spawned a Marauder on my first 2 skull mission (enemy reinforcements on a destroy Convoy side mission), which I ended up salvaging completely, then proceeded to build a headshot Marauder. Then one or two missions later (a Flush Them Out city battle side mission) spawned in Atlas, which was my first assault mech, followed by a second Marauder and a Cyclops HQ. So even before getting the SLDF Highlander I was already steamrolling through the game. Still, the peak of the game for me was an incredibly fun 5 skull Proxy War mission which was a glimpse of what the game's mechanics are capable of. Proxy War is an Attack and Defend mission (so you have to destroy the enemy base in time of else it will keep spawning new reinforcement lances), with the complication that the enemy base is defended by powerful turrets, and the no man's land is a battle royale between two different OpFors (Directorate and Liao). So basically I had to pick two mechs of my lance to sprint behind the Liao side in 3 turns, while my two other mechs perched on a cliff to referee the battle between the Directorate and Liao to make sure neither side dominated the other side. Even still my Atlas and Highlander got shot in the back by the Liao Atlas a few times (inexplicably) and I was pretty lucky to get through the battle without anyone losing a limb or a torso.
Proxy War - the peak experience of Battletech for me. I was very thankful for it was finally over with no one getting blown up.
This would be as close as I would get to losing this lance. The Atlas got roughed up bad.
Glorious wreckage isorla.
So my impression is that the expansions have solved some of the performance and gameplay issues of the game on launch. The game ran pretty smoothly on my 7th gen Intel i5 SSD laptop, although the heat starts to go nuclear about two minutes in (but the laptop does that with other programs too). Gameplay-wise, I think the expansions added a lot more variety to the side contracts like Attack and Defend, Proxy War and Pincer (where you have an NPC ally lance) so the missions have more twists to them. Having a lot more mech chassis to choose from also helps, although it probably takes too much rare components to pimp out a sweet Annihilator or Warhammer before finishing the campaign. They do make the battles more interesting though, since they spawn even in the campaign missions. Enemy Archers are a big pain in the ass, Marauders need to die immediately, and enemy Cyclopses increase the challenge of any battle where they are present.
Still the game has the same issue as Shadowrun Hong Kong, since the new toys unbalance the game ultimately making the challenge trivial. Both the Marauder and Cyclops gave my lance such a huge advantage that it really killed any of the challenge of the last few campaign missions.
I am now replaying from the start on the hardest settings (hardest spawns, mech components to 8, stingy payouts and salvage, etc...). I am also playing without giving my mechwarriors any experience gains and without modifying mechs from the basic loadouts. It seems to be like Age of Decadence in that you have to gimp yourself to make the game challenging enough for the experience to be satisfying. I think that will at least help prolong the game's sweet spot by delaying the staleness of completing an endgame lance of heavy/ assault mechs too soon, although it could be counter-intuitive since much of the fun of the game is in collecting new mechs and customizing them in mech bay. But on the other hand, being able to optimize mechs while the AI can only play with the basic loadouts is really what kills the game's challenge (ok the AI is kind of meh too). However, I think that the game as is on the default setting already maximizes it for "fun" and making the logistics of the game more challenging and frustrating probably doesn't make the game better. Sadly, there is no easy way to solve the ultimate issue that the game's AI cannot hope to challenge a pimped out endgame SLDF heavy/ assault mech lance even with huge numerical superiority.
I actually unlocked the Black Market right before Coromdir and found the components to complete my own Atlas II. Victoria got her King Crab gangbang assfucked. When your lance is 2 Atlas II, a Marauder and a Cyclops Z, it's time to retire. Is there a point to playing anymore?
I think it should be easy to make a simple mod that a) generates side contracts where you fight alongside 1-2 NPC controlled allied lances from your own company, so that you can have larger battles and have use for more than just 4 mechs and 4 mechwarriors and b) lets the AI spawn with some more optimized loadouts to make the battles less lopsided.
I also have some thoughts on the game's balance as a whole, but I might save that for later. While the basic balance between ballistic, energy and missile weapons is a little off from CBT, I think overall Battletech translated the feel of tabletop Battletech successfully. It feels like tabletop wargaming.