There are some obvious things to do, that might make it slightly more possible:
1. Right now, it is considered bad to start or end the rotation on the ice. There should still be 5 rotations in the air, but the torso could start rotating on the ice, and you could start to go into landing position after hitting it (the latter is sometimes already true, but I think they deduct GOE points.)
Change that, for quints, and that would effectively leave you a lot more time in the air to complete the rotations, that isn't spent slowing down or speeding up those rotations.
2. Make more bouncy soles. There is a clear trade-off here: the more bounce, the less control. Put people on big shock absorbers, and it is obvious you wouldn't have the precise control needed for figure skating. I'm not sure where the break even point would be, but I am pretty sure other skating skills would suffer first if you add much more bounce.
I have tried to find information on USFSA and ISU websites about rules for boots and soles. AFAICT, for the most part, there aren't any. That's not quite true: they have to have a single blade with two edges, and the manufacturer's visible mark can't be too large - but that says nothing about bouncy soles, or even about mechanical aids - though if people started using mechanical aids like spring loaded devices, gas shocks, powered exoskeletons, etc., I assume it would be banned very fast. Maybe it already is, somewhere I haven't looked, e.g., in IOC regulations.
In many other sports, people use bouncy soles in their shoes. In fact, if you buy a good pair of sneakers (tennis shoes, running shoes, basketball shoes, aerobic shoes, cross-training shoes, etc.), they probably have them.
In theory, bouncy insoles/footbeds are easier on the body, and reduce injuries. Unless, of course, you use them to jump higher - which is of course exactly what I am suggesting.
Most materials have some bounce - including some used in current skate boots. This is only a matter of degree.
3. Drugs. There will always be some performance enhancing drugs that aren't yet banned. I assume they are quietly marketed to or developed for elite athletes or coaches.
4. Anything that would make it possible for guys to do quints might make it possible for gals to do quads - I think only one gal has ever succeeded in competition.
5. Right now ISU rules do not give any benefit for doing quints - they aren't in the rules at all.
(See
https://isu.org/isu-statutes-constitution-regulations-technical/special-regulations-and-technical-rules/52-2016-special-regulation-sandp-and-ice-dance-and-technical-rules-sandp-and-id-final/file - you can find point values if you search for "quad" but not for "quint")
I don't know enough to know whether that just means they would be credited with a quad, with some deductions because they aren't perfect, or whether they would get no points at all - but the rules would have to change.
6. It isn't clear the rules committees SHOULD allow quints - if they will cause more injuries. There are already a lot of injuries in figure skating. A few years back, a University of Delaware study said that most elite figure skaters that they tested were skating with bone fractures. Some of the people at the Olympics, this time and before, are skating competitively WITH injuries, including some of the best.
It seems nearly certain that more and more difficult jumps WILL create injuries. What is more, if people are allowed to rotate on the ice before and after landing without major penalty, that will increase the torque on the lower body, which could greatly increase injuries.
If more women could find a way to do it, it would happen to women's quads too - though brittle bones are more common in supremely athletic women then supremely athletic men (look up the "female athletic triad").
In practice, if some do it, and get extra points for it, the others must, to remain competitive. That's what has happened for men's quads, and what, some time past, happened for women's triples.
7. An interesting independent question. I remember reading somewhere that figure skaters who spin very fast get red hands, because some capillary blood vessels break, from centrifugal force. Is that true in fast aerial spins, or do you have to spin longer? How long does it last?