@alah did not ask about "many AVR MCUs". He asked a specific question about two specific tiny processors.
I meant more generaly.
If you had taken the few seconds necessary to follow the link I posted you would have found that the opening page of the website includes a list of cores appropriate for tiny processors including Mark Sproul's core.
I have already taken some time to look at your site, but I don't think if I need to repost the links.
His core is incomplete for tiny processors. There are much better choices available.
I must say you are right with that, but the way Marks core files (and the new with that the new ones released with the new IDE) are made on register basis, meaning it's easier to add more MCUs. Can be that your core files are that too, but I haven't looked at them more than with a glance.
JanD