That's a problematic amount of flexibility. For example, there are a lot of out of combat spells that overlap what other classes do. Invisibility, Knock, Longstrider, Unseen Servant (for setting off traps), Detect Thoughts, etc. Heck, Disintegration. Being able to not only mimic much of what another single character can do, but being able to replace for multiple classes since it's any spell in your book - that really steps on toes.
Add in things like regular fly spell on a melee combatant, renewed all day, regular divination, and other things of that nature can really impact the ability to run adventures.
And this gets to be even more at higher levels. Imaging casting Wish to duplicate any other 8th level spell with just a minute or 2, as often as you want during the day. Cast Foresight without taking up your 9th level slot. Antipath/Sympathy - lasts 10 days, no concentration or expensive material component. How many Clone and Simulacrum spells can you cast in a day? Everyone in the party Mind Blanked every day.
And that's just looking at the beginning and end of the list. Most of the meat of the spell lists I haven't looked at.
I think I might not have explained well (again, thanks for helping me clarify). In my system wizards could “hang” as many spells as they have time but only cast a spell out of combat as a ritual, limited by their slots available each day. So, for example, it would be impossible to renew fly all day. It still only lasts 10 minutes, you still have to concentrate the whole time, you still lose 1 3rd level or higher slot each time you cast it. Even a 20th level wizard only has 3, 3rd level slots per day. That also makes the wizard no better at taking over roles of other classes than in RAW. The number of slots they can use to actually cast the spells is the same.
I did mention before that I expanded the exhaustion system to 10 levels and allow wizards to make a hard ability check to cast another spell beyond their daily limit but even on a success it costs a wizard a level of exhaustion. The check is progressively harder to make so, at most, a wizard might be able to greatly weaken themselves and cast maybe 5 more spells per day, at a progressively higher risk. So I’m not really thinking its an unbalancing problem.