The struggle is the high level regulatory bodies (with the exception of aberrations such as the current admin's approach to appointment) generally select for individuals with a low risk tolerance. Low risk tolerance is generally incompatible with speed - it's a miracle the covid vax and treatments were approved as quickly as they were in 2020.

Biggest example of this risk aversion is the peptide craze going on (the most famous of which are GLP-1 antagonists). It's pretty much a wild west where people read a low-sample animal study, and buy a drug that's "for research only, not for human consumption" off of a compounding pharmacy in China.

Few human studies because even if you have willing and enthusiastic volunteers it's too expensive and creates legal liability. And the FDA cannot approve it without a high bar of evidence (for effective treatment and low risk) and costly, time consuming reviews. Because of this, there is a black market for the things and people are basically being their own test subjects.

What you say is something that is actually already happening.

There is no longer a binary approval/non-approval status. Drugs and treatments that address terminal conditions often get special status. Drugs for rare diseases definitely get special treatment.

In addition, many studies now use continual data collection and evaluation. If the results are very good or very bad, that can be recognized much more quickly and with fewer people exposed to risk than previous types of studies. Reaction to negative events doesn't happen in hours, but it isn't all that far from that.

This does happen. SAEs are reported in real time, and they do halt trials sometimes. Also, there is often a condition of approval that requires ongoing data collection for adverse events post-approval.