One thing I absolutely loved about Halo was the fact that you could customise almost every detail of a gamemode.

Such as the moving speed, jump height, gravity, spawn times, weapon starts/pick ups, health/damage etc...

Is Brink going to have the ability to mess around with the settings in custom games?

jump height and gravity probably not.
jump height because you would be able to go out of bounds, and gravity because it wouldn't fit the setting

I expected that

First and foremost, because it would lead the bodytype-movement-restraints ad absurdum.

BRINK is well thought through and can't simply be changed in this way or another.

it would be cool, but bear in mind that the multiplayer is also the story. They have to literally explain the weird gravity or increased running speed.

There is a gamemode that lets you adjust game settings, but it has only been mentioned so we know next to nothing about how much you can change or if this is even in anymore.

Well, there's challenge mode..?

To be honest, given how complex the objective based missions are currently I'm not sure what you would actually be able to customize?

For me, I'd kill, er... strongly urge for a Capture the Flag game type. It seems almost perfect given the movement types and S.M.A.R.T. system.

It will pop up from time to time as one of the objectives so its there never fear.

But the flag would probably be intel or a defector of some sort. Like Resistance stealing key intel and have to run it back while security tries to kill them and take it back.