There was much discussion about possible Olney's lesions (which don't seem to occur acutely at any recreational dosage a human could ever take) and that benzodiazepines would protect against them, but also dull the experience. Clonidine might be the better agent for that, and it could be that it'd actually add to the experience, countering the stimulation - as Solpisis already said, ketamine is actually more of a stimulant (and a neuroprotective one to some extent) than a downer (while it indeed potentiates opioids, but this is somewhat complicated)! But this makes dissociatives so uniquely physically safe amongst all drugs in my eyes, as long as you don't mix them too much.
I miss MXE so much, it had just the perfect ratio of 5-HT, DA and NMDA (maybe even endorphin/enkephalin) activity. But it was a bit too psychotic in higher dosages, yay, so not recommended to 'hole' on it - but a combo of MXE + K makes a really good time. And nothing is able to top MXE as an antidepressant at low dosages ... it's really not addictive and probably not toxic too.
Here in Europe it's currently not hard to source really good ketamine again if you know where ... this has been much worse a year ago or so. But yes, it's expensive and probably they're controlling all much more than they should (if you ask me, that is). The resources'd better be spent otherwise. Taking down these heroin and cocaine cartels, or the political corruption and war. Financing science and all that.