[squeek.]

Remove concs on spawn:

function player_spawn( player_entity ) 
   local player = CastToPlayer( player_entity ) 

   player:AddHealth( 400 ) 
   player:AddArmor( 400 ) 

   player:AddAmmo( Ammo.kNails, 400 ) 
   player:AddAmmo( Ammo.kShells, 400 ) 
   player:AddAmmo( Ammo.kRockets, 400 ) 
   player:AddAmmo( Ammo.kCells, 400 ) 

   if player:GetClass() == Player.kScout or player:GetClass() == Player.kMedic then
      player:RemoveAmmo( Ammo.kGren2, 4 )
   end
end

Hmm.. for the not giving concs on cap... try this:

local basecap:oncapture_base = basecap:oncapture
function basecap:oncapture(player, item)
	basecap:oncapture_base( player, item )
	
	if player:GetClass() == Player.kScout or player:GetClass() == Player.kMedic then player:RemoveAmmo( Ammo.kGren2, 4 ) end
end

I haven't tested either of them, but hopefully they work. The second one is particularly experimental because the "traditional" method of doing it would be to overwrite basecap:ontrigger which is not a good idea.