The MAMEception Challenge:
How many different emulators (not just MAME, but MAME is preferred; let's open this up so people can have fun with really weird combinations) can you chain together in order to get back to an old version of MAME (within the first year of its creation) running Pac-Man?
I am still waiting for a standardized formal language for automatically handling nested emulators (also for hardware drivers), including an AI for recognizing and cross-compiling them transparently in the manner of a JIT. For software archeology and longterm preservation such a tool will eventually become essential, when knowledge gets lost and people those wrote the only existing earlier emulators have died decades ago.
Although it currently sounds out of reach by appearing far too complex and inefficient to be automatized, remember that not long ago ChatGPT was considered sci-fi either. I think of something as strictly formalized as a Turing machine (or at least as the LaTeX scripting language), but to make it efficient enough would be undoubtedly hard. (I am not sure if Moore's law is still valid and future quantum computers may mitigate this.) A first step would be a standardized API to control emulators from outside. An algorithm (e.g. as part of the OS) should check if it can run a software natively. If not, it needs to delegate that to its "universal" emulator, which should recursively try the same by delegating it to lower layers (i.e. emulators running on emulated CPUs) until something compatible is found. In an ideal world those lower layers have to follow the same API (if not, a translation layer is needed). A major problem here may be even the 1st check for native executability, because CPU generations can differ in such subtle ways that it is hard to verify, since old optimized machine code can e.g. get messed up by pipelining in ways those crash it only randomly (happens e.g. with Win98SE 32-bit device drivers on 64-bit PC CPUs inside VirtualBox).