But it does nothing to lower the hourly running costs - which is what is needed.
For 70k euro less to buy, you can spend that 70k on maintenance and higher fuel usage.
Let's say you save 5k/year on maintenance. Let's say you save 5 liters mogas / hour. Let's say you do 200 hours / year. Mogas is 2 euro/liter here (avgas is already 3 euro/liter, that's over $15.7/gallon!). So that's 5k + 200*5*2 = 7k/year savings in favor of the LSA. Then you have the 5% interest rate at which you could have put your 70k away, that's 3.5k/year.
Net result is the LSA will save 3.5k/year when flying 200 hours. That's a break even after 20 years of flying, assuming no deprecation on the 100k initial investment of a new LSA vs an old C152 with mogas STC. My guess is that if you maintain the 152 properly for the next 20 years, it'll be worth the same as a new LSA flown for 200 hours/year for 20 years.
If you fly less than 200 hours/year, then you would even need more flying years to financially justify a new LSA.
So I don't understand your quote that the hourly rate must go down. Yes, the less money spent per hour, the better. But the initial cost of capital is huge.
And the downside of any EASA certified plane is you still have the part m requirements.
Yes you could go experimental, but if you have any intention of renting it to others or use it for training, you need a certified plane.
So from a financial perspective, a 150/152 is still the preferred choice. If you can manage 1000 hours/year, it might be different, but I suspect most schools in my neighborhood are happy if they can sell 200 hours/year/plane.
So yes, if an upgrade of a 150/152 is desired, then I think it's a good investment. Nice panel (not necessarily glass) and good looking seats, new paint, decent avionics, and you are set for the future.