Upgrading photographic equipment, freelance photographers and professional photographers really ask for help.

I suggest you go to D5 and choose some commonly used lenses. You don't need so much. You can rent it for a few days, or you can exchange it with a new one for a common one, or you can buy a second-hand one instead. For wedding photography, customers still look at the guy, and a big guy who looks very professional may attract some users. Forget the D750. Almost like an amateur. The number of wedding photographers here is at least 5D3, mostly 1DX.

I wish you change your equipment and go uphill!