This is a no brainer.
If you are buying the real estate at current market value,and getting the equipment and "business" for free, buy the real estate and move the operation to your current location and sell the newly aquired building and come out with the business and equipment for free.
As far as your business plan, if you are rolling the old operation into your existing operation, cut all of the management, accounting, lease, and utilities expenses out of the P&L of the company you are aquiring.
Go ahead and add the added revenue you think you can achieve and work toward that goal.
I have been saying for years the sales projections that people use for business plans are pulled out of thin air and banks know it. They just need some figures to look at.
Hell, if it is like you describe....if you don't do it, I will.