Alternatively, maybe I should run several instances of electrum with separate wallets based on appending alpha, bravo, charlie, etc to the original seed phrase. Will it let me do that?
You can:
[1] Set a different derivation path for the second, third and fourth account for alpha, bravo and charlie wallets.
Generate a "
BIP39 seed" offline and create an Electrum wallet (
Standard wallet-> I already have a seed) by enabling "
BIP39 seed" in the "
Option" below the seed text box.
To set the derivation path for the second account, select the address type and (
for legacy) change
m/44'/0'/0' into
m/44'/0'/1',
m/44'/0'/2' for the third and so on.
This is technically the same as your "
old solution", but this time it's Electrum.
or[2] Generate a "
BIP39 seed" offline and set a "
BIP39 passphrase" for alpha, bravo and charlie wallets.
To set a BIP passphrase, enable "
extend this seed with custom words" above "
BIP39 seed" and provide the BIP39 passphrase in the next window.
Different passphrase will generate different "
wallets" (
note: BIP39 passphrase is not the wallet's passphrase).
The obvious security flaw here is having a single seed for all the businesses' funds is dangerous.
Once the seed or one wallet was compromised, it's only a matter of time for the other wallets to get hacked,
Specially the first option that can all be hacked instantly once the seed was compromised; the latter will depend on the strength of your BIP39 passphrases.
For the main idea: using a brainwallet is a very bad idea;
If you really want to use a single seed phrase, I recommend the BIP39 passphrase method instead.