Is there a way to set which weapons a player spawns with on my server?

whell i don't exactly know what you mean, but i think u mean this
LINK (http://jediservers.bsgaming.net/help_articles_weapons.asp)
hope that helped ya

An interesting question. I think by default the weapon values are stored in the gametype (but I could be wrong, I'm not a Q3 coder).

Normally players only start with a BlasTech pistol and Lightsaber (or Saberstaff, or Dual Sabers or Melee). In JediVsMerc (which is a switch that can be applied to any gametype virtually) you can either start with a Lightsaber (or Saberstaff or Dual Sabers) or playing as a "Merc" you'll start with a BlasTech, Melee, ST Rifle and Bowcastor.

In Siege you have different classes set to begin with different weapons on different maps on different teams. ; )

So it may also be stored in the maps themselves. So you may need to create your own gametype or a new map with new values. Sorry I can't be more helpful...

The weapondisable command will only limit what kinds of pickups are on the maps in question on your server (so disabling Det Packs would remove all Det Pack pickups and not let you use them).