D&D 5E Do you allow Bladesingers to cast Mending, Shillelagh or Magic Stone as part of the attack action?

[Xetheral]

I think the See Invisibility analogy is being misapplied. The root issue that makes that spell so controversial is that the Invisibility condition grants disadvantage on incoming attack rolls twice: once for being unseen (heavily obscured) and a second time as an explicit effect of the invisibility condition.

See Invisibility explicitly lets one see invisible creatures, and (contrary to what's been argued in this thread) that is enough to negate the disadvantage on attacks from the invisible creature being heavily obscured. But the independent source of disadvantage from the second bullet point of the Invisible condition is unaffected, so (as the argument goes) See Invisibility doesn't negate disadvantage on attacking invisible creatures.

Accordingly, I don't think the correct takeaway from the See Invisibility kerfuffle is that the spell is insufficiently specific (and therefore that 5e in general requires super specificity). I think the correct takeaway is that the Invisible condition was poorly written, inadvertently granting its benefits twice.

In any event, I think it's a mistake to draw system-wide conclusions on the level of specificity required in 5e from a single controversial developer ruling.

 

[UngeheuerLich]

It breaks in-universe logic.

So a high level fighter attacking 4 times as often as a low level one, or a fighter healing 1d10+fighter level hp every hour does not? The in-universe logic is that some people have abilities that seem to break normal limitations...

It doesn't need anything apart from a general warning to ignore RAW when it does not make sense.

You are free to do so.