Wouldn't recommend a track specific frame. They limit your use to track wheels with track wheel specific freewheels like the white industries
freewheel. There are a lot of crap freewheels on the market, and they wont last long. WI are some of the best ones, but they are expensive. And if you want to change from lets say a 16T to a 17T, you need to buy another one, and as said, they are expensive. Much better to buy a road frame and use road wheels with single speed conversion kit.
This way you'll easily be able to change to another cog, and you'll be able to use all kinds of road wheels, which you'll often find without braking the bank. Besides that, road hubs are usually more durable than freewheels, even the WI ones. If you choose the conversion solution, you'll need a chain tensioner os well.
This way you'll have a lot of frames/bikes to choose from. And if you're willing to buy second hand, the options are unlimited.
If you insist on the ready build single speed with option for big tires, then take a look at the On One Pompino. Cheap and a good bike. Lot's of options for fenders and racks as well. If you want it with discs, it's the On One Pompetamine you'll be looking for.