While your proposed efforts are appreciated, there is no way that any official support would could be revived for low flash/ram devices.
The current requirement of 8/64 is just barely sufficient, and the next major release will drop this in favor of 16/128.
It is the kernel itself that is largely responsible for increased resource requirements. And the kernel comes from upstream -- it's not like the OpenWrt project is artificially inflating the kernel.
There are community 'tiny' builds that are not "official" but provide recipies to fit more recent versions into older hardware. For example, see this one. However, those assume that the platform target includes the devices in question... your device was not moved from ar71xx > ath79, so there would be quite a lot of work to try to get it running, as this target shift was significant in nature and happened many years ago now (I can't answer why that specific device wasn't transitionted -- maybe the 4/32 size, or maybe some other issue came up).
As an academic exercise, there's certainly no harm in trying, but you're unlikely to get much, if any help with the development, and the work you'd put into this effort would only have the educational value and/or in the cummunity builds section insofar as it wouldn't be integrated into any more recent official builds. All versions pre 23.05 are now EOL and unsupported -- no backporting of devices (or anything else) will happen on any official build. But, if you are able to successfully build for your device on ath79, you'll certainly have learned some serious tricks in coding efficiency.
Therefore:
- For your own educational purposes, sure, go ahead and try... but...
- Don't expect any help since no currently supported build could fit, meaning you'll be working with unsupported/EOL builds. Further, it is not recommended to use unsupported/EOL builds due to security vulnerabilities which will never be patched.
- Even those volunteers that may be willing to help may not remember the nuances of the older versions and the ar71xx > ath79 transition, so any help may or may not be fruitful.
- Your work on such an old device would have benefit only to you and your specific device and unofficially within the community builds.
- IMO, it's not worth the effort, but I recognize this may be more about learning than practicality... thus:
- it doesn't necessarily mean it isn't worth doing for fun/education, but I think most people would recommend putting that effort into adding support for a new, more capable device so that it can be of more universal appeal and move the OpenWrt project further in terms of supported devices or even better new target architectures.