More 401(k) choice spells demand for advisers.

* Brokerage 'windows' add diversification, but hand-holding is needed

The seemingly simple design of 401(k) plans has changed direction -- and it bodes well for companies that provide investment advice for plan participants.

Over the past 18 months, a growing number of 401(k) plans have started offering self-directed brokerage accounts, or "windows."

Those accounts allow employees to put some of their retirement dollars into investments that fall outside a standard plan's 10 or so available mutual funds.

While the accounts provide gre