Having layers of weapons and equipment enriches the universe and keeping things from getting stagnant. Try looking at it another way. What if tank designs didn't change after WWII? We wouldn't have the Abrams. We'd have a variant of the Sherman made up of everything that goes into the Abrams. Now at what point does tech stop advancing? The end of WWII? 1950s? Can we have any variant as long as it could be built with WWII technology? Or do we have a hard cut off date?
Kind of reminds me of Girls und Panzer. Which we can do in Battletech. It'd be the box set mech only introtech rules. Which is fine for some and there's nothing wrong with that. Girls un Panzer didn't stop with WWII tanks though. They didn't even stop with the original tank types. They've continually added more tank types, even WWI tanks. They also have MBTs and other unit types. Just like BattleTech didn't stop at mech only introtech rules or with the units found in TRO:3025. It's continued to grow. That's a good thing for those players who don't want to be limited to a certain unit type, tech level, or era.
And the thing is even if canon says something goes extinct that doesn't mean that players have to stop using it. By having "bloat" players can play along with the canon march of time or be free to pick and choose what we want. At least we can as far as the list goes. We can't pick something that doesn't exist, without going into house rules. But we can do things like have Blazer Armor in 3025 or QuadVees with Rifle Cannons, or Periphery built LAMs because they cost less than the more modern alternatives.
Without "bloat" I don't think we'd be here. Which is probably the best reason for "bloat". I think the trick, and it's a pretty big trick, is to manage the bloat. We do some with availability dates, and with rule levels. Dates work when playing with canon time periods.
The thing with rule levels is that things go down in level but I don't think I've ever seen them go up. That means the list for Tournament level is constantly expanding. I'm okay with that but clearly not everyone is. Which is okay. I happen to think that items need to move from Tournament up when they stop being standard items. When that'll happen I don't know. And maybe rule levels as a whole needs a look at?
I think this is the heart of where you and I disagree. I understand what you're saying, and I certainly respect your right to have and voice your opinion, but I completely disagree with the logic here on several levels.
First of all, you aren't divorcing Battletech the game from Battletech the universe. I am 100% fine with Battletech the universe mentioning whatever the heck it wants to. One-off designs, oddball weapons, deadend tech, angry tax collectors, whatever. Let the next novel be about a guy who has modified an autocannon to fire ball-peen hammers if someone thinks that will make Battletech the universe more interesting.
But Battletech the universe is not Battletech the game. Battletech the game needs to be approachable, and the more sidegrade medium lasers you add to it because they were mentioned in the last sourcebook, the less approachable it becomes. To say nothing of the fact that layers and layers of equipment aren't interesting in and of themselves. Especially if they all do basically the same thing with relatively minor bonuses and penalties to distinguish them from one another.
Second, I just don't think you're correct. Again, your obviously welcome to your opinion, but I think your opinion is wrong. I don't think there is ANY evidence to suggest that a game that retains the same basic set of weapons and equipment remains stagnant. If you need more evidence of that than the fact that CGL just made $2.5 million on a Kickstarter campaign centered on the second most basic period of the timeline, look no further than every WWII game ever.
The usual rules of talking about Battletech still apply, of course. Its your table, and your game, so do whatever the heck you want. Frankly, I love your passion for the oddball tech and your inclusion of it in your campaigns. I'm sure it makes for memorable games. But on this topic, I think Nicoli hit the nail on the head with this reply earlier:
The bolded line is the problem, people trying to make core Battletech into something that would work as a D&D campaign. You want something weird to give your players during a campaign let the DM, make it up and have it be for that campaign or put it into a campaign only book for DMs. Flooding the core boardgame with a bunch of nice stuff if you want to run a campaign where people play the same exact unit over and over again is not going to be good. Campaign rules and stuff for it should ALWAYS be separate from the regular pick up rules and should have no impact on the design of the core rules. This isn't to say that one way is better or the "Right way to play" but as you pointed out they are really two competing goals in a game system and your just going to end up either losing half your player base or all of it if you try to incorporate both as one.