I imagine re-ordering is a big problem. The only application I can think of that would require a single flow is media streaming, but you only need ~4Mbs for a decent quality stream anyway. Other applications like file transfer can be split into multiple concurrent flow, at which point you might as well just let the local router nat each flow to each internet connection in turn.

I routinely ship 50mbit media streams over the internet, and sometimes streams up in the 200mbit range. In campus streams are up in the 10gbit range.

Over bonded networks bitrate are typically under 40mbit, and usually under 20

Of course none of this uses tcp.