Yes, there appears to be a PATA port that you could connect to a HDD or an optical drive to (as the Ultrabay does), but by definition an PATA "line" has a lot of pins (I count 16 data pins plus several others).
I don't have an Ultrabay, and that's too many wires for me to fit inside the case so I haven't played with it.
If you have physical room or want an external drive, there is
this, which allows you to connect a SATA drive to an IDE port.
While it would make a cool experiment, I don't see much sense in it though. You'd either need to make something that sticks out of the bottom of the machine to access the Ultrabay connector (in which case, why not just USE the Ultrabay?) or solder something like 30 wires to the motherboard. While possible, that would be a major pain and a lot of trouble.
Solder on BGA is too difficult for me
There's nothing to solder unfortunately. The two other SATA channels actually just have their RX pair grounded and last I checked none of them even emerge from under the chip.
If you want a 2nd HDD, read threads
here and
here and a few others. It'll give you some ideas of what's been tried and what works.
Do you have any particular goal you'd like to accomplish?