We have done this for a client because they needed more deduction room. The owners could have also used to load up on CB benefits but interestingly chose not to do so.
You'll need to comply with prevailing wage (PW) law, so immediate entry and vesting, and deposits at least quarterly (probably same in DC). The potential downside is you have a defined contribution credit amount (3% per your thoughts) - if someone's PW was less than 3%, you still have to credit 3%. If you're leveraging for cross-tested HCE benefits, now you have to provide gateway.
For my client, we have a 5% credit because we needed the deduction room, but some people worked partially on PW projects, but mostly on non-PW, so ended up getting more than they would otherwise. This was not optimum, but was sacrifice worth the added deduction and HUGE cost savings on payroll taxes that would have been due if paid out as current compensation.
Whether in a DC or CB, employees view this money as their compensation and you'll see them requesting their distributions the day after they terminate even with the 10% penalty tax. Then, if this is a seasonal industry, the following year/season they are back working and it starts all over.
Admin on these arrangements is a bit more involved than your standard CBP. Good luck.