2.6 already has that. Weapon limiting per team is enabled by default (yellow below); you only have to enable the global weapon limiter switch, and set the limits (green below). See weaponcontrol.cfg:
//******************************************************************************
// weapons limiter
//******************************************************************************
// You may wish to use a fixed number of a particular weapon available per game.
// Here you can set a limit per map for each of the COD2 weapons. Optionally per team.
// Make sure your preferred weapons are enabled in the Weapons section (scr_allow_xxx).
// A limit of 0 will disable a weapon completely.
// Max and default for weapons and grenades is 999 (= unlimited).
// Remember, if you wish to use any of these settings, uncomment and set the
// global switch, and the weapon you want to limit.
// Ensure you leave enough weapons for the number of slots your server holds.
// Global switch
// 0 = disabled (default)
// 1 = enabled
set ex_weaponlimit "1"
// Limits per team
// 0 = disabled (weapon availibility is on a first come, first serve basis)
// 1 = enabled (default)
//set ex_weaponlimit_perteam "1"
// sniper rifles
set ex_springfield_limit "1"
set ex_enfield_scope_limit "1"
set ex_mosin_nagant_sniper_limit "1"
set ex_kar98k_sniper_limit "1"
set ex_g43_sniper_limit "1"