2 teams with same weapons

Imagine a game where there are 2 teams and these 2 teams have the same properties, like those in RTS. Both teams have the same weapons that can damage each other the same way, etc.

What kind of approach should I go for if I am going to do this in Construct Classics?

Have a private variable dictating which team the weapon belongs to, and for any events dealing with damage make sure the condition for dealing damage is that the weapon's Team ID is different from the defender's Team ID.

You could try this example:

scirra.com/forum/tbgs-top-down-combat-ai_topic44874.html

I made that awhile ago, it could help as an example. But I wouldn't advise using an exact copy of the system, it's fairly buggy.