Yeah I agree. Perhaps more varied puzzles involving the runes too (rebuild a dam gate using magnesis, halt a water wheel with cryonis, go into a cave system using bombs etc). I really miss conventional Zelda fishing too!
I know I go on about Xenoblade Chronicles a lot, but that game changed open world games for me. And it's a relevant talking point here as 100 of their staff helped on this; I think this game is essentially those two games mashed together, with added physics.
BOTW takes a lot of XC's strengths and nicks them; using twinkling items to guide your way around the land, fast travel, infrequent but dense towns, unique enemies per area of map, sense of isolation amongst the beautiful nature, quest logs, collectopedia and heart-to-heart affinity side missions (basically memories in this game without XC's fetch quests). Despite running everywhere, crossing huge terrains also never got boring.
Thematically there are also crossovers; use a glowing blue sword to take on some ancient mech who have turned against humanity; you'll need your finest gear to do so and approach combat differently.
The main difference to BOTW was that the map unlocked gradually and definitely halted your progress at times, as the epic linear story had marks you needed to hit. So you felt confined to one big area at a time.
XC X did away with that and followed more of BOTW's open Hyrule structure. Start in a city hub, learn the basics, go explore. Like XC before it, it got away with this vastness by using the memorable scenery to pique your interest and stop you feeling directionless. But after 40 hours, once you'd unlocked the map and done the 10 story missions, repetition set in. The systems in that game are more explore, collect, fight so once I'd found all the landmarks, I was done. What drives most XC X players on was collecting the most amazing gear to take on the crazy overpowered enemies you see lumbering around; this never spurred me on personally but I think it would have done in Zelda, given the games more varied ways of earning rupees and gear.
But yeah... I think a future Zelda could stick largely to this formula but inject a bit more story, some meatier side quests that fill in pivotal characters' back story, perhaps introduce a rune upon completion that opens super rare shrines, cut the shrines down to 50 longer challenges and have higher level enemies in there for the end game. Then it's close to perfect.