It's nowhere near 'old'. Anything before Fallout 1 is old (1997).
To your predicament, first off you can customize your debugmenu at your leisure. Second of all, you can use as many codes as you like. Here's what you do:
You hit escape and work your way through the menu, expanding it. You click one code, say infinite ammo.
Hit escape going back to the game (can't remember if that's necessary, think it is). Hit backspace to collapse your debugmenu.
Hit escape again and find another code you want to use.
I'm looking at the file right now;
<'GOD PLAYER',GOD PLAYER>
<'SETBIOMODSLEVEL 3', SETBIOMODSLEVEL 3>
Bio-energy options are in there too. Any questions?
Gryphon, unfortunately due to the way the DX2Menu.ini is laid out it would use up more than the 6000chars limit for posts on this site. However, I recommend that you paste the following at the very bottom of the DXUI .ini file, not the DX2Menu.ini.