I believe it's mostly a bang per buck think though Jon
Most people are not after the last 0.01g of corner force
What they want is something cheap and easy giving massive improvement for minimal outlay.
Then, for the 205 at least, there's the issue of lack of choice. There simply aren't off the shelf parts out there that allow the real level of tweaking required.
Look at my old mini for eg. That had adjustable everything and it all came off the shelf. Rosejointed, coilovered etc etc you can just go to miniworld (for eg) with circa 500 notes and walk out with a completely adjustable setup
Certainly on the 205 there's no option to do that at so you end up looking at customized builds which is going to cost a fortune
Unless you happen to be, well, you lol, with a nicely setup experimentation workshop to convert stock parts into bespoke you have to get someone unfamiliar with the car to build parts with unpredictable results.
Sure you can go to Leda etc etc and they will build you a nice set of adjustable struts. But they will also be in the dark regards spring rates, damping rates etc etc and getting this right is going to needs loads of trial and terror. As you know you can get into the ballpark with book numbers but gitting it right is a matter of carefully controlled experimentation. Very time consuming and more potential outlay on new springs, dampers etc etc.
Then there's the kit required. Ideally corner scales are going to be needed for setting ride height, adjusting for driver weight etc etc.
A 4wheel alignment is really necessary multiple times for a given damper setup to tweak max performance
It can mostly be done "on the cheap" but it takes huge time and effort and you still need several accurate sessions on a proper alignment setup to perfect it.
I used to have all sorts of jigs for basic mini tweaking. I had gurtmongous poles which bolted to the hubs allowing accurate setting of toe. You could work out thrust angle too. Then there was the camber gauges. Accurate setting of this was really only possible because we had a scissor ramp back then giving guaranteed points of reference, especially combined with the tailor made car cradle which bolted to it. I never ever figured out a way to reliably DIY caster though. Sure it could be done
I'd set up the suspension to something that seemed about right then dial in the geometry. Then go out and drive it, usually with horrible results. Then come back and bin all the "think it should be right settings" and start again until I had the damping set up about right feeling. Then began all of the the geometry tuning with that damper setup. It took weeks and weeks of widdling about to get anything close to an ideal feeling setup. If I had G sensing logging you could probably have multiplied that even further since (from my experience) the absolute optimum paper setup rarely seems to suit an individual driving style. For eg I tend to go a little understeery so I enter slow but tend to come out fast etc etc etc etc. Everyone else wants a slightly different feel from their car which suits them
Once I'd got all that set up "just so" I'd still always have to go back to the tyre shop for a 4wheel alignment, corner weighting etc etc to actually make everything perfect.
I was lucky in that they "sponsored" me with free access to their kit otherwise it would have cost me hugely
All of the above also excludes simple settings like tyre compunds, pressures which only serve to make setup issues worse lol
And all of that is in a lightweight car that intrinsicly handles better than the 4 and about which there is a huge wealth of setup info to get you started. It just gets worse when you throw a hugely nose heavy naturally understeery 4WD package into the mix
Plus I must confess I make assumptions that probably aren't right. I tend to expect that people have checked the basics and upgraded the basics before they start asking questions simply because that's what I would do.
Bearing all that in mind I think it's quite possible to suggest a setup for "average Joe" based on what's available and based on the goal.
For eg, JP wants a nice trackday setup which works on the road too and which largely comes out of a "handling improvements" tin
The choices are quite simple. TRD springs and dampers, whiteline adjustable rear ARB and a good check of all the suspension linkages to eliminate any play. Then throw an average alignment into the mix and you're going to have a car that handles much better than stock for minimum (lolololololol) outlay. For a slightly more adjustable setup then go with the Tein coilovers
Jon wants something which might possible be competetive in a race series. Clearly the above JP setup will work but won't be ultimate. You're going to be looking for more spring choices, wider damping ranges, more geometry adjustment etc etc
A proper adjustable coilover setup is really the only way forward to allow proper corner weighting, height adjustment etc etc. Youre going to want either re-valvable dampers or more ideally fully adjustable remote resevoir jobs mated to superstrut casings
Full geometry adjustment will be needed either through bespoke suspension arms or at least adjustable topmounts and/or camber bolts (yuk)
At this point track rubber means you'll be needing to strenthen/de flex all of the stock bushed to remove unwanted geometry changes due to mountings.
You'll end up with a car that handles beautifully (within the intrinsic chassis limits) on track but is a right pain in the proverbial on the potholed barely maintained surfaces that are the UK roads