There is currently a rather major issue with Slice Immunity, and it's unfortunately a difficult issue to work around. Here are the problems:
When the player is covered in Berserkium they take self damage from the Omega Sawblade entity.
The Vulnerable debuff causes the player to lose their slice immunity, thus making Giga Discs and Omega Sawblades deal self damage.

Here's more of a technical explanation for any modders reading this:

The standard disc projectile is a normal projectile with self damage turned on, so it's easy to alter the projectile's ProjectileComponent to not have self damage when cast.

For Berserkium the issue is that Summon Omega Sawblade is an entity that can attack the player like any other allied entity if the player is covered in Berserkium. I don't know whether to call this a bug or not because the spell name clearly states that you're summoning something, not casting a normal projectile.

For the Vulnerable debuff the problem is with Giga Disc Projectile and Summon Omega Sawblade, which have AreaDamageComponents attatched to them. These don't have a friendly_fire value, and I don't think this component even keeps track of its caster. Your only option is to alter its entities_with_tag value, which defines what entities is can damage. Problem with that is that there's no value that can exclude an entity with the player_unit tag, so you would have to create a new tag for every enemy that doesn't have 100% slice immunity. The problem with that is that you have to alter almost every enemy in the game, and that takes a lot of time, and if another modder overwrites a enemy sawblades can't damage them.

If anyone has any advice for handling these issues in a way that maintains general compatibility for the mod, please let me know.