accountable plan for S Corp owner/employee and bonus depreciation

"Client purchased truck in 2022 and plans to use it about 75% for business in his construction work"

Which is why it should not be a corporate vehicle. The nonbusiness use is taxable to the employees through payroll, and that's a pretty significant amount of nonbusiness use.

"He completes the proper reimbursement form under an existing and implemented accountable plan for his S corp and wants to take advantage of  Bonus Depreciation in 2022"

He would turn in for Mileage, and the rate includes a component for gas, oil, maintenance, insurance (general operations) and wear-and-tear (depreciation).

"Lets assume that the reimbursable amount under bonus depreciation is about $50,000 (75% of the purchase cost)"

Are you trying to pass as expense his actual costs under an accountable plan, then?

Are you trying to sell that vehicle to the S Corp under an installment plan?

Are they wanting to lease the vehicle to the business? Because that is a circular reference and creates taxable income (and insurance risk) for that owner, as this no longer is a personal vehicle.

Some people try too hard to get too tricky, and totally overlook some great provisions that already exist.