It's possible indirectly in native. You can eg. modify damage, ranged damage, accuracy, reload speed of agents (based on weapon they use):
agent_set_damage_modifier = 2091 # (agent_set_damage_modifier, <agent_id>, <value>), # value is in percentage, 100 is default
agent_set_accuracy_modifier = 2092 # (agent_set_accuracy_modifier, <agent_id>, <value>), # value is in percentage, 100 is default, value can be between [0..1000]
agent_set_reload_speed_modifier = 2094 # (agent_set_reload_speed_modifier, <agent_id>, <value>), # value is in percentage, 100 is default, value can be between [0..1000]
agent_set_ranged_damage_modifier = 2099 # (agent_set_ranged_damage_modifier, <agent_id>, <value>), # value is in percentage, 100 is default
You can also do your own damage formula, working only for specific game mode (like in DTV adding 110% damage to Flamberge, 135% damage to Danish Greatsword, 152% damage to arbalest, 125% damage to all bows and so on). But you can't change item stats just like that AFAIK.
However, if you use WSE, it adds additional functions, which allow you to change important stats:
item_set_thrust_damage = 3828 #(item_set_thrust_damage, <item_kind_no>, <value>), #Sets <item_kind_no>'s thrust damage to <value>
item_set_thrust_damage_type = 3829 #(item_set_thrust_damage_type, <item_kind_no>, <value>), #Sets <item_kind_no>'s thrust damage type to <value>
item_set_swing_damage = 3830 #(item_set_swing_damage, <item_kind_no>, <value>), #Sets <item_kind_no>'s thrust damage to <value>
item_set_swing_damage_type = 3831 #(item_set_swing_damage_type, <item_kind_no>, <value>), #Sets <item_kind_no>'s thrust damage type to <value>
item_set_head_armor = 3832 #(item_set_head_armor, <item_kind_no>, <value>), #Sets <item_kind_no>'s head armor to <value>
item_set_body_armor = 3833 #(item_set_body_armor, <item_kind_no>, <value>), #Sets <item_kind_no>'s body armor to <value>
item_set_leg_armor = 3834 #(item_set_leg_armor, <item_kind_no>, <value>), #Sets <item_kind_no>'s leg armor to <value>
item_set_speed_rating = 3835 #(item_set_speed_rating, <item_kind_no>, <value>), #Sets <item_kind_no>'s speed rating to <value>
item_set_missile_speed = 3836 #(item_set_missile_speed, <item_kind_no>, <value>), #Sets <item_kind_no>'s missile speed to <value>
Of course, server need to use WSE to get those functions working. Since cRPG servers uses WSE, it shouldn't be a problem in cRPG
.