Uh, i cant think of a way how to pick a secondary without the player doing an command/speak action.
It would look like this, but you would need to add a dozen of strings to prevent them doing it after they spawn/pick their weapon.
function OnCommand(ID: Byte; Text: string): boolean;
begin
if Text = '/111' then begin
ForceWeapon(ID,GetPlayerStat(ID,'primary'),1,0);
end;
Result := false; // Return true if you want to ignore the command typed.
end;