There is no other ITR form is specified. If assessee has only Interest income ITR-1 will be filed. if assessee is non-resident then that column will be ticked.
And forms are also classified on their simplicity and applications....its like you can't put salary income under the head income from business/profession right ???
He may even authorize any person to sign the return on his behalf as authorized representative.
A useful development in the recent years is the facility of online/e-filing of returns which helps timely filing. However, if he does not have a digital signature, he will have to adopt a combination of e-filing and physical submission of the return filed online within 15 days of e-filing.