Not a bad idea - but how best to arrange it and implement it . . .?
Admittedly, that's kind of what I have in mind - it's just managing to not make it impossible, while still making it properly challenging.It doesn't have to be, though. Who said it'd all go well? Especially after First Year, I'd expect the bank to have some sort of extra traps and guardians set up for its vaults, and it's pretty well accepted, if not just established, that the Lestranges did something nasty on top of that. The gobbos are pragmatic enough that it doesn't have to just be magical stuff, also. I'm thinking "Mission Impossible" type laser grid equivalents, magical tripwires loaded with mundane chemical payloads... and on top of that, having to get in and out without tripping enough alarms that the Goblins get distracted from the disaster topside.
Yeah - as I said, I've seen it done; it's just not what I'd like to do - too easy.