Yeah, there's no good reason to settle for an invalid checksum. If you input a 24 word phrase in to iancoleman which has an invalid checksum and then click "Show entropy details", it will automatically change the final word to the correct checksum, maintaining the same 3 bits of initial entropy.
That's actually a pretty neat feature of that BIP39 tool... Just need to pick a word that uses the same initial entropy as the N bits of entropy leftover (7 for 12 words, 3 for 24 words) and then pad it out to 11 bits, then click "entropy details" and it'll correct it to the correct word!So, basically, an offline copy of the BIP39 tool and a coin... and one can randomly generate mnemonics to their hearts content, knowing that they don't need to worry about "bad" RNGs (assuming their coin isn't biased!
