Is there a way to mod starting sovs weapons?

Yes. With xml.  The easy way would be to swap out whatever weapon he has in <AutoCreateEquipment> tags with your choice from coreweapons.xml  (located in game's english / data folders ) .

You can make your own weapons as well if you want to check "use mods"  and then can save all kinds of stuff in your mods directory. 

I prefer to do it that way than modify my core files.  So when I uncheck "use mods" I've got clean vanilla game again.