Howdy! I'm a new dev looking for anyone who has some understanding on a few niche components.
I'm more than willing to pay for a working implementation of any of these half-baked ideas.

Swapping ParticleSystem[] within Flamethrowers, or any component.

A functioning LiquidWeapon with no held entity. I've gutted the RPC checks and I can get the damage logic, but no particle effects.

Toolgun Beam between entities without a held item generating the hitinfo.

Parenting a mortarblue to a player with functioning networking, or creating an alternative way to make a BaseFirework.

Parenting objects to animal NPCs without having them lose their AI.

A way to spawn looping prefab effects.

A list of valid gun_fire_effects and a way to swap them.

A way to retrieve the bones of an NPC.

Using WhiteThunder's ParentEntityRenderFix for everything already.
If you know anything about these ideas, or if you know I'm coming at something wrong/futilely, feel free to post or PM me.

"A way to spawn looping prefab effects."
Just calculate approximate lenght and loop it?

You can get bones with .GetModel().boneNames.

Thats awesome info zug! I've just been foreach parsing SkeletonProperties.Bones[] for players and was interested if there was a way for other entity types.

When it comes to playing looping effects, I'm talkin about the ones that won't even spawn without some component.

"Tried to spawn an effect without a EffectRecycle component (assets/prefabs/effects/foliage/pfx_leaves.prefab)"
Not really sure how to announce the variable and give it the component before executing Effect.server.Run.

Seems like no spawnable prefabs are even using this when looking at the OrangeWulf ent dump.

I use "assets/prefabs/effects/foliage/pfx_leaves.prefab" on my server for when people teleport out of a location. You have to create it as a entity and give it a transform.position.
So youd probably do something like on the hook of the recycler. Create it. Move/scale it to where you want it to be using the recylcer as the location start point. Remove the default effect then use a timer to continue to check that the recycler is active. Then remove it afterwards.