I don’t think there’s an ARPG that appeases both types of gamers (Seasonal/non-seasonal).
It’s usually completely one sided.
However, we already know what works and what does not. No reason to reinvent the wheel.
You can do it the way PoE does, but, again, why? We already have PoE. Why copy its systems?
PoE is completely season-based. Non-seasonal realm is a dumpster and nearly nobody uses it. That’s because the new hot stuff is ladder only.
Then we have Grim Dawn, which is completely non-seasonal.
Then we have Diablo4 which fails at both models.
How about making both realms attractive for once?
If players aren’t done after two weeks because there’s nothing else to hunt for, you’ll make eternal/non-seasonal realm attractive to those who want to enjoy the new content, but at their own pace instead of racing.
Playing eternal would be appealing to people who want to slowly build up the character.
This requires two things: chase items (that are unlikely to drop over a single season/cycle) and “uber” content/dungeons/bosses that can challenge even minmaxed chars to give the players a goal.
That would make seasons very exciting (only the very best would be able to clear the content in 3 months, which is the purpose - to give people a challenge), but also, for those who don’t have that much time to play a single game for hours every day, there would be an option to complete the content over time.
This would literally make everyone happy. And it would be the first ARPG to do so.