Patineuse élite et professionnelle
Why? I think it's the most important question which always seems to be forgotten in such discussions.
I, for one, don't see any need to extend (or shorten) careers of athletes. Moreover, any special rules or artificial manipulation of any kind trying to interfere with sport rules known as "stronger, higher, farther" or natural "survival of the fittest" system - is seed of corruption and detrimental to the sport. Because it brings personal bias where is no place for it.
I can understand such a viewpoint from fan of particular skater perspective. However it can't be sufficient justification for changing rules - because rules meant for everybody. From whole system point of view there aren't any skater who is more deserving than other, or more worthy etc. They all are equal, they all have the same rights. However, trying to extend careers of ones - you are shortening careers of others, Why? It's simple - there are always only 3 places on podium. The longer one skater is encouraged to staying in sport by putting him on podium instead of others (giving him artificial advantage such as reputational PCS judging, artistic programs, increasing age limit etc.) - the shorter will be careers of less known athletes since they will start to lack motivation. It's good result for particular "stars" fans - but it's very unfair for others. I can't call such system anything but corrupt. Sport should be just and impartial - it's my deep conviction.
As for special tournaments for "oldies" only - be my guest, give them a go. However I think you are forgetting one important thing - as a fan you want to see them as long as possible. But will they want that too? Did you ask them about it? After certain age in fs there are lots of injuries and health problems accumulating in one's body. Majority of those who ended their career - did it exactly due to health issues. Will any new rules or competitions be able to bring them back? No.
First of all---regarding Pro only competitions. That's not going to hurt anyone. And we're not "oldies" thank you very much, we're pros. Many of us are like 30 something years old. Not old at all, we're all hardly ready for the retirement village. And yes, many of the pros do want to still compete, there's just no outlet right now to do so. And many of us did not end our careers due to health issues. Yes, there are some that do, but it's not the majority. I know, I live day in and out in this skater world. I have competed and done shows and so on with in it, I'm not of the fandom side, and can speak first hand on it.
ETA: Here are the choices as skaters we have right now when done eligible competition: Show skating, coaching, choreography (if that's ones thing), rink management(etc) or go outside the sport and find something else we can do, and even many of those that have done that route end up back in skating in some shape or form.