Building a lan PC, do I need an internal dvd drive?

I'm building a pretty unique computer right now, and it's mainly meant for being taken to different places to game on. Most of the games I play are steam games, so always having an optical drive with me isn't very important.

BUT I might be persuaded to sell it if I get any good offers, so my question: Should I take the time to come up with a place to put the optical drive? I'm building the entire computer in a briefcase (monitor included) and it would be much easier to fit everything if I didn't have to worry about it. I don't know how many games these days require you to have the discs in while you play them, so I guess that would be the deciding factor.

So what do you guys think, take the time and try to cram a drive in there, or take the easy way out and just rely on an external drive for installations?

If your gonna use an external, at least use esata and not usb. Use an elecctronics technicians hard case and you'll have a lot more room for stuff, you could fit an internal in there easy probably.