HaloFromSteam

Yep, that's right.

Now, go to steamapps\common\portal 2\portal2\, and open up pak01_dir.vpk in GCFScape
Oh, and also anywhere outside your mod folder, create a folder called pak01_dir. Really. That.
Now, create ui\basemodui in your mod's resource folder.

So, when GCFScape is open, go to resource\ui\basemodui.
Go open up mainmenu.res with a text editor, and also go copy and paste it into \resource\ui\basemodui. Now, rename that to mainmenu_new.res
So, first, let's change: (This is for the Single Player Button)

"labelText" "#PORTAL2_MainMenu_Solo"

to:

"labelText" ""

Mine is just:

"labelText" "Play Single Player."

Now, change:

"command" "SoloPlay"

to:

"command" "Extras"

To make it jump into the extras button.

Now to remove the co-op button.

Text Code:

"BtnCoOp"
{
"ControlName" "BaseModHybridButton"
"fieldName" "BtnCoOp"
"xpos" "88" [$GAMECONSOLE && ($GAMECONSOLEWIDE && !$ANAMORPHIC)]
"xpos" "63" [$GAMECONSOLE && (!$GAMECONSOLEWIDE || $ANAMORPHIC)]
"xpos" "88" [!$GAMECONSOLE && $WIN32WIDE]
"xpos" "63" [!$GAMECONSOLE && !$WIN32WIDE]
"ypos" "310" [$GAMECONSOLE]
"ypos" "288" [!$GAMECONSOLE]
"wide" "220"
"tall" "20"
"autoResize" "1"
"pinCorner" "0"
"visible" "1"
"enabled" "1"
"tabPosition" "0"
"navUp" "BtnPlaySolo"
"navDown" "BtnOptions"
"labelText" "#PORTAL2_MainMenu_CoOp"
"style" "MainMenuButton"
"command" "CoopPlay"
"ActivationType" "1"
}

Also, keep the original .res file open from the .vpk file. You'll need some things from there later on.

Now, remove the extras button.

Text Code:

"BtnExtras" [!$GAMECONSOLE]
{
"ControlName" "BaseModHybridButton"
"fieldName" "BtnExtras"
"xpos" "88" [$WIN32WIDE]
"xpos" "63" [!$WIN32WIDE]
"ypos" "348"
"wide" "220"
"tall" "20"
"autoResize" "1"
"pinCorner" "0"
"visible" "1"
"enabled" "1"
"tabPosition" "0"
"navUp" "BtnOptions"
"navDown" "BtnQuit"
"labelText" "#L4D360UI_MainMenu_Extras"
"style" "MainMenuButton"
"command" "Extras"
"ActivationType" "1"
}

Now, remove the Robot Enrichment Econ.

Text Code:

"BtnEconUI" [!$GAMECONSOLE]
{
"ControlName" "BaseModHybridButton"
"fieldName" "BtnEconUI"
"xpos" "97" [$WIN32WIDE]
"xpos" "72" [!$WIN32WIDE]
"ypos" "420"
"wide" "220"
"tall" "20"
"autoResize" "1"
"pinCorner" "0"
"visible" "1"
"enabled" "1"
"tabPosition" "0"
"navUp" "BtnQuit"
"navDown" "BtnPlaySolo"
"labelText" "#PORTAL2_MainMenu_Econ"
"style" "BitmapButton"
"command" "EconUI"
"ActivationType" "1"
"bitmap_enabled" "vgui/store/store_button"
"bitmap_focus" "vgui/store/store_button_focus_anim"

Now, time for the navigation.

So, first, find:

"navDown" "BtnCoOp"

And replace that with:

"navDown" "BtnOptions"

NOTE: This is where you need the original .res file...
Below, for the Options button, you will have to remap that as well. So... find:

"navUp" "BtnCoOp"

And replace it with:

"navUp" "BtnPlaySolo"

Save that file now. Go to \bin, drag that pak01_dir folder outside your hard drive onto vpk.exe, and copy and paste the pak01_dir.vpk (The one you just created) into your mod's folder. Restart Steam and test it!