You may want to consider starting an S-corp (mainly for the self-employment tax savings) to be used as the management company.
You can then create individual LLCs as you see fit.
Your S-corp will invoice the LLC's for a management fee; and you pay yourself out of the S-corp. Be sure to recognize the tax benefits of distributions from your S-corp.
There are horror stories about people who have tried to recategorize their income as distributions on top of nominal below-market salaries in order to avoid self-employment tax. It doesn't seem worth it.
This doesn't avoid the (federal) self-employment tax, since you still have LLCs in the mix and the owners would pay taxes on their LLC income. Also, you end up with worse taxation at the state level. (Why does everyone forget state taxation? Only a few states don't have income taxes.)
Also, assignment of income (by the LLCs to the S Corp) would not prevent the IRS from taxing the LLCs on the income. If it did, everyone would do this and this would be the recommended tax structure for every multiple-project business.
Finally, when dealing with related entities (businesses which have the same owners), the IRS has significant leeway under the law to disregard the form of transactions and tax based on the economic substance of what is really going on. Which means the IRS could disregard the S Corporation entirely.
You can then create individual LLCs as you see fit.
Your S-corp will invoice the LLC's for a management fee; and you pay yourself out of the S-corp. Be sure to recognize the tax benefits of distributions from your S-corp.