Yeah, we should definitely be thinking about how each of these options might play out long term as well.
The Dream Idol too is something I'd be worried about offering - it a) would likely be noticed, and b) could look like we're trying to mess with the spirit is some kind of complicated and Problematic
TM way. And indeed *could* very well influence the spirit.
I guess the problem with the brush though, is that if we're worried about us offering power to the spirit making it stronger and disrupting the ecosystem, then the brush could be even worse? It is a 4th realm talisman after all. I'd assume that the spirits can get power from offerings like that as well, though we don't know much about the mechanics there.
@yrsillar is there anything you could add about what LQ would know about how offerings of power and items etc. could affect spirits?