How come it won't take away the players control? [READ DESC.]

There are 2 good ways to take away control from Players. The first way, is to disable "ControlScript" inside game.Players.Player.PlayerScripts. When you want them to have control of their character again, enable the script and they will be able to control their character.

Another good way is to assign controls over the default ones. You could use the following script:

local ContextActionService = game:GetService("ContextActionService")
function onKeyPress(actionName, userInputState, inputObject)
    -- None of this stuff in this function is actually necessary. But it's good for reference!
    if actionName == "A" or actionName == "<" then
        if userInputState == Enum.UserInputState.Begin then
            print("A was pressed")

        elseif userInputState == Enum.UserInputState.End then
            print("A was let go")
        end
    elseif actionName == "W" or actionName == "^" then
        if userInputState == Enum.UserInputState.Begin then
            print("W was pressed")

        elseif userInputState == Enum.UserInputState.End then
            print("W was let go")
        end
    elseif actionName == "S" or actionName == "v" then
        if userInputState == Enum.UserInputState.Begin then
            print("S was pressed")

        elseif userInputState == Enum.UserInputState.End then
            print("S was let go")
        end
    elseif actionName == "D" or actionName == ">" then
        if userInputState == Enum.UserInputState.Begin then
            print("D was pressed")

        elseif userInputState == Enum.UserInputState.End then
            print("D was let go")
        end
    elseif actionName == "Shift" then
        if userInputState == Enum.UserInputState.Begin then
            print("Shift was pressed")

        elseif userInputState == Enum.UserInputState.End then
            print("Shift was let go")
        end
    elseif actionName == "Space" then
        if userInputState == Enum.UserInputState.Begin then
            print("Space was pressed")

        elseif userInputState == Enum.UserInputState.End then
            print("Space was let go")
        end
    end
end


ContextActionService:BindActionToInputTypes("A", onKeyPress, false, Enum.KeyCode.A)
ContextActionService:BindActionToInputTypes("W", onKeyPress, false, Enum.KeyCode.W)
ContextActionService:BindActionToInputTypes("S", onKeyPress, false, Enum.KeyCode.S)
ContextActionService:BindActionToInputTypes("D", onKeyPress, false, Enum.KeyCode.D)

ContextActionService:BindActionToInputTypes("<", onKeyPress, false, Enum.KeyCode.Left)
ContextActionService:BindActionToInputTypes("^", onKeyPress, false, Enum.KeyCode.Up)
ContextActionService:BindActionToInputTypes("v", onKeyPress, false, Enum.KeyCode.Down)
ContextActionService:BindActionToInputTypes(">", onKeyPress, false, Enum.KeyCode.Right)

ContextActionService:BindActionToInputTypes("Shift", onKeyPress, false, Enum.KeyCode.LeftShift)
ContextActionService:BindActionToInputTypes("Space", onKeyPress, false, Enum.KeyCode.Space)

When you want to unbind the above script, use the following:

ContextActionService:UnbindAction("A")
ContextActionService:UnbindAction("W")
ContextActionService:UnbindAction("S")
ContextActionService:UnbindAction("D")

ContextActionService:UnbindAction("<")
ContextActionService:UnbindAction("^")
ContextActionService:UnbindAction("v")
ContextActionService:UnbindAction(">")

ContextActionService:UnbindAction("Shift")
ContextActionService:UnbindAction("Space")