Floor drains are required by most plumbing codes to be connected to the building drainage system and building sewer. They are required to be trapped and vented.Minimum size is 2".Vents must be installed within 8 feet of the trap.Consult your local plumbing code office for details.
There are many modular flooring company's who you can buy from to create a danceable look. If you want it done in epoxy, then you will need an experienced industrial coating company to install it for you.
You need to make the surface of the current floor rough so the new floor will expand and contract at the same rate. Best to remove the old, but if you are going to put at least 3" thick of new concrete, you can put it on top.