After doing some occasional fiddling with Rego Vim in campaigns, it seems to me that several of the guidelines are somewhat clunky to use in practice, and that it should be possible to achieve a new guideline via Original Research that streamlines it for certain particular purposes, but isn't out of line with the RAW level of power that is assumed.
My troupe has several lovable but unrepentant optimizers, so my thought is to get my thoughts down here and get input before proposing it and getting clowned on.
Rego Vim Guideline:Mystically entangle two similar objects, such that they are magically considered the same object. Any magical effects which affect one will affect the other, at level+5 magnitudes. Arcane Connection is considered default, otherwise the entanglement will break when used out of range. Magical effects exceeding the strength of entanglement only affect the object directly affected. If the objects are dissimilar, such as a wooden statue and a stone statue, only magical effects which can target both are transferred.
Ex:A ReHe levitation spell cast on the stone statue has no effect on the stone or wooden statue. That spell cast on the wooden statue causes it to float, but has no effect on the stone. A CrIm to cause items to emit light causes both to begin glowing.
Caveats:
Magic resistance is an interesting beast here. My inclination is to require effects to penetrate based on the targets magic resistance. So if you have a paired set of rocks, but one is under Aegis, an effect on Rock A would affect A, but without penetration would not affect B.
However, I could also see a possibility for allowing it to bypass magic resistance, since one needs to penetrate with the initial ReVi spell, and probably penetrate again if you use it offensively with a Arcane Tunnel. Commentary requested on this.
It would also presumably have interesting effects with more explicitly magical objects, since my initial inspiration was a separate enchantment allowing MuVi effects from one enchanted object to affect spells from a different enchanted object, so long as they both were linked at the time of enchantment(of both the MuVi and target effect), probably with the ReVi enchanted in, requiring one or both to be Invested Devices.
It is also magical entanglement. Casting a ReAn on entangled quills causes both of them to write. Picking one up with ones hand does nothing to the other.
Justification:
I don't believe this does a lot that cannot be done with somewhat more clunky setups with extant guidelines. It incorporates the same spell power restrictions as Arcane Tunnels, and more or less adheres to the arcane conduit guidelines that seem to allow for it.
It functionally builds a sort of Arcane Tunnel between the two items.
Now, while it is true that it seems to allow one to cast a spell on two separate objects with one individual, my inclination is to have the spell split penetration like in the case of the Wizards Fork, and otherwise let it be. Could use input on that.
There is also a concern with plausibly using it to create something like Arcane Connections between objects on the fly, even more close than regular ACs.
But, the spells do have expiration times. My personal inclination is to treat it like spell containers generally, and Watching Ward specifically. That is to say, a permanent/nonexpiring entanglement requires either a ritual or an enchantment, and a vis investment either way. Otherwise the entanglement expires with duration or dispel.
On the subject of RDTs, the Range would ideally be the range at which it functions. Yes, I know that is bizarre and not usually how the range works, but for this, the effect would be functional if the entanglement is used within the range the spell has. So if you cheap out and use Sight instead of Arcane, you can affect the objects with stronger spells, but it would necessarily require the objects to have line of sight. I am undecided on this, but I honestly think my fall back would be to make Arcane mandatory. Or else nerf the level+5 mag thing if it is unworkable so balance isn't broken.
As before, I don't know that there is anything particularly cheesy that can be done that cannot already be done with a bunch of Arcane Connections and corresponding Arcane Tunnels. Perhaps a blanket ban on use with ritual effects to dodge the obvious magically entangled warehouses that are CrTe filled with gold(though I think that doesn't work by default, something about room and structure disallowing creo ritual cheese in the core book iirc).
But I could be terribly terribly wrong, and would be looking for input on this.