You should create your own thread and ask all the questions you want there
You should take a look at cell-mans kits,
The Pie is a good motor but it's heavy and is a bitch to pedal, but if you don't mind that, then the pie can take a lot of power as you can see from this thread!
Yes you can mount disk on the motor but chances are you will need to use a spacer or 3-4 m5 washers to give the clearance between the disk and calliper and motor!
cell-mans mac 500 is a lot smaller and can do 29-31 mph max on an infineon controller with the 120% speed setting in the controller, on 44 volt 12S LiPo, or 25-27 on 10S LiPo,
The mac is also much easier to pedal because of the free wheel!
Also you would be much better going with cell-mans A123 LifeP04, which can supply high power setups, Golden Motors batteries are fine if you want to use their controllers which are not capable of more than 15-20 amps and you will find yourself wanting a lot more!
In the end we all want more power and if you get a battery that can't give out the amps, then you have wasted a lot of money to begin with!
I would go with a LiPo battery set up, but that is complicated if you have not used LiPo before!
Back to pedal only power.