I can't see any case in which is this "too much" of a boost for Sorcerers. They're a weaker class than other spellcasters, by and large. They're vastly weaker than Wizards. This would help them - it won't fix them, and indeed the other stuff for them is mostly just mucking around charmingly than boosting their power, but it's the right direction.
With Bards, I think you can't make a reasonable case that it's "too much" except with level 7/8/9 spells, because they know sufficiently few of those, and they're sufficiently dramatic that I could see limiting them to changing out spells of level 6 or below, and perhaps being allowed to change out a 7/8/9 spell with a month's notice or something.
I feel like your analysis doesn't really look at how Clerics are already rather more powerful and flexible than any of these guys, whilst wearing good armour + shields, having decent weapons, and in many cases having extremely good non-spell abilities.