We should consider removing foreign_account_inputs field from the TransactionArgs (TransactionParams) or replacing it with something else. The main reason is that most of the data contained in this field should go into the advice_inputs (e.g., account witness, SMT paths etc.). This is done during the TransactionAdviceInputs creation here. We'd still have the ability to add foreign accounts, but these could be "broken up" on insertion. For example:

pub fn add_foreign_account(&mut self, account: AccountInputs) {
    // TODO: add account inputs to self.advice_inputs
}

Another option would be to get rid of the most foreign account data from here entirely and load it via the DataStore interface.

Originally posted by @bobbinth in #1426 (comment)