Let's put it this way:
The "slots" a mech has are what an engineer can work with during mech design. For example, you only have two slots in your Center Torso, and twelve on each side torso. These are your limits for what you can put where. It's why no matter how much you want to, even the Classic Battletech mech design rules don't allow you to put a Gauss Rifle on your mech's head.
It's likely that you can ship your factory-model mech to a mech shop and have it fully customized, kind of like when you send a car you just bought from a dealer to your fave mod shop for souping up. This could take time, depending on what you want. Your tech, like your car's mechanic, will give you a ballpark figure for the number of weeks or months it could take to make your specified mods.
We who fight in MWO should consider the customization we have as BATTLEFIELD mods. When you look at your mods that way, the hardpoint system makes sense.
Ordinary battlemechs have limits to what mods you can do to them on the fly in the field. Let's say we're in our dropship, having just been spit out by our jumpships at a pirate point. If you don't have the luck/rank/pull to pilot an Omni, you have to go with what you have. Your tech will tell you that they can probably swap out the PPC for, say, a Pulse Large given your timeframe but they're going to shake their heads if you want a Gauss Rifle installed there. The electronics and general design of your battlemech just can't hack it, given the time.
From what I know about the lore, this is why Omnis are such devastating platforms. The first time Clan Coyote fielded them, their enemy thought they were using a set config and deployed to counter that config. The Coyotes ran back to their dropships, swapped pods, and creamed their opponents.
Not all mechs are Omnis, unfortunately.
So, yes, limited customization of BATTLEMECH hardpoints sounds BT "canon." It makes sense, actually.
You want almost-unlimited customization, wait for the Omnis, I guess.
Edited by Rion Raios, 11 September 2012 - 04:06 AM.