[IngvarLynn]

>modeling it after a general cryptocurrency is probably a bad idea

Not modelling after but integrating of an existing one. Because this saves massive amount of engineering effort.

>rising prices may prevent legitimate clients from being able to connect to onion services due to the challenge being too expensive

Obviously, the price for legitimate clients would be much cheaper, as their requests shall be placed in the middle of priority queue (clients can wait a few seconds) while the attacker have to occupy the very top of this queue all the time. Also note that the bigger the DDoS in this scheme - the bigger profits server could make, which he could spend on expanding capacity.

>each visitor contribute to a partial solution that can then be combined to derive funds

This scheme predates monero, which was about 10 years ago.

>the next generation learns from our senseless technology-burnings.

Not if they would reinvent the wheel each time instead of adapting of existing tech to current needs.