Timebender I could see how you could pull it off, but not headrush (and it wouldn't be the same sound, like you said, but similar in idea). I've gotten the dd-5 close before too with some outside help (idea-wise...But it had a different character). I have an amdek flanger that I think has an LFO problem that can get really close with a short delay after it (still more chime-y though). However, I still think misty cave has a vibe all its own. There are certain pedals that it can act pretty mundane with in the context of a setup and clean can be kinda not very fun.
There are combinations with the misty cave that are just amazing ... When trying to something similar with the other pedals, there is a lot of character and swell lost too (like the koma can do the metallic thing, but it is way more harsh, hard to dial in, and just missing that something special). It's an odd one and the effect doesn't always work, but it is pretty distinct misty cave when it is at full bloom. However, I haven't tried a misty cave work-a-like on the timebender (or something like nemesis).
Misty cave always sticks out as one of the more unique and distinct effects that I have...The similar in concept but not exact sound thing may not matter in a long chain anyway....But I only use like max 4 pedals ever (meaning I could see the overall character of the misty cave being lost in a longer chain...I think it kinda has to do its own thing ).
I always play loud and through my beta lead...Never headphones...Don't know if that makes a difference

I think some of the misty cave work it does is pushing air and then making some physical feedback which spikes the resonance.
But headrush, nah...Not at least the e2 I had.