a bunch of text that people won't read, but should... (mm. It seems dollar sign symbols don't work in quotes. There goes my attempt at wit, right there. The 'S' on should was totally going to be one. Dammit.)
See, I get what you're talking about. I get the whole 'silhouette' thing, and I know it's really important to the game. It's what makes it fundamentally different from CS:S (other than the silly)... you can't really tell the difference between a Deagle and a glock at long range, but you can sure has hell tell the difference between a huntsman and a rifle.
However, I think the idea of addons would be a 'cheap' way of accomplishing what you're looking for. Nothing game changing, of course; I know you're looking for more weapons like jarate or the sandvich (or movable buildings) that completely change the face of the game. I certainly wouldn't mind them either; gives us brainy types something to play with on the intellectual level. However, that takes a lot of work on the part of valve.
Look at the pain train. That's a pretty
mild weapon. an effect that's only useful on certain maps for 10% more damage from bullet based weapons. Why couldn't that be something that attaches to another weapon? Saves about 8000 polygons in the game (reducing player-side memory usage) and you could switch it around just as effectively.
I don't really know what item could give you those effects, from a 'making sense' point of view (I wouldn't have called it a board with a nail through it, but here we are), but it wouldn't kill them to include a viewmodel with that as well. A laser sight, as I mentioned in my previous post, wouldn't be hard to make a model for; it could be small and low-detail, and just stick on the side of the weapons or whatever; they're work out were the 'addon' slot would be on the weapon.
But here's my core issue. I like what you're saying about new weapons... already talked about that. My only issue is things like the pain train. that whole weapons just reeks of 'meh'. Nothing groundbreaking about it, nothing particularly provocative. It's boring. Theoretically speaking, it's interesting to talk about, but in practice, if I'm looking for a way to change up my gameplay experience, I'm not going to pick that. I'll pick something like the eyelander, or even the skullcutter if I'm looking for variety because they're fundamentally different from the bottle.
What I DON'T want is a bunch of 'meh' weapons. Weapons should be distinct and interesting, and as far as I'm concerned, when talking about a given slot of any class, you should never get to say "well let's get x out of the way right now; it's lame, and isn't worth talking about." New weapons, to me, mean new, interesting functionality that make the game different, and offer REAL choice when it comes to the player. My suggestion is that we take all those 'meh' weapons, and turn them into options that AREN'T weapons. hence, addons.
Think of it this way: New weapons should be game changing. addons are there for the 'min-maxers' of the TF2 world, who want to tweak their weapons to fit their precise playstyle with existing weapons. they aren't meant to change the game; They're meant to customize it, and fit the individual player just a little bit better.