Using margin instead of a home mortgage

I'm interested in utilizing margin to withdraw some money to fund a home purchase. The interest rates on Interactive Brokers are quite low at around 1.5% and I believe I have the capital and risk tolerance for it. I am particularly interested in hearing of anybody who's done this or if anybody has recommendations or advice.
Here are the details:
$2.5 million invested in a diversified selection of stocks currently in a cash account.
~$900k purchase price for an apartment in NYC. Monthly taxes come out to $700 and common charges are $600 per month.
Other assets:
$1 million in a Merrill Lynch wealth management account. It's invested in stocks, bonds and commodities.
A $800k house in NJ, fully paid for.
A $800k commercial building in NJ with a 10 yr mortgage at a 4.5% rate. $400k is paid for. A $300k commercial property in NJ, fully paid for.
The reason I'm looking into using margin is that I can get access to a better interest rate (although I understand it can go up in the future). Additionally, I won't have to liquidate any of my current holdings. Finally, I believe I can save some money on the purchase by making an all cash deal and not paying closing costs. Another advantage is that I can "pay off principal" by reducing margin debt as frequently as possible and that if I ever feel like partially pulling out of stocks for a bit I'll save a bit on interest. Also, if I plan on upgrading to a better apartment in a few years it would be easier to do than with a regular mortgage. It just seems like massive win vs a traditional mortgage given that I'm able to bear interest rate risk and would only be borrowing a small chunk of my total assets.
Thanks for any help you guys can provide, I appreciate it.