Participants never vest due to nature of jobs

A small company's industry is that of leasing its employees to other companies for their specific projects, so its employees typically don't work for it more than 18 months, and aren't typically re-hired. My understanding is that the employees understand this when they're hired. Therefore, even though employees become eligible for profit sharing contributions due to satisfying initial eligibility requirements, most of them terminate with 0-20% vesting under the 2/20 schedule. There are around 30-50 NHCE participants and a few HCEs.

It seems to me that there could be BRF "effective availability" issues, partial plan terminations (though that's "facts and circumstances" and it could be argued that the terminations are voluntary), and the Form 5500 reporting of large #s of partially-vested terminees could be an audit flag. And just the general design seems clear that it's intended to circumvent nondiscrimination rules to only benefit the owners, and the government would view it that way in an audit even if there's not a black-and-white violation.

The "safe harbor" plan option for Leasing Organizations (100%-vested MP plan, that allows a recipient organization to exclude such Leased Employees) may indicate that the IRS wants to avoid this type of scenario.

Maybe an ERISA's attorney's opinion that this specific employer's employee terminations are voluntary and don't create annual partial plan terminations, with a caveat to the employer by the TPA that it can't ensure that the government may not approve if the plan were to be audited, would help?

Also, I'm wondering if a vesting schedule was chosen where most participants at least partially-vest, or if they're receiving a 3% Nonelective Safe Harbor contribution, would give them a meaningful benefit that may help.

I'd appreciate any input on this.

Thanks.