Contributions to a qualified plan by a sole proprietor are excluded from gross income but subject to self employment taxes. If that sole proprietor sets up an LLC and elects to be taxed as a corporation, can they avoid the self employment tax? What if they are the only member?

Entities taxed as corporations deduct employer FICA contributons as a business expense.

And it is my understanding that LLCs taxed as corporations issue W-2s to the owner/employee. That would also overcome the problem of the owner not having income for plan purposes in a year when the business has a loss.