It is way more complicated than this because in any heterogeneous network environment you need to be really careful about what happens then you have new protoco

It is way more complicated than this because in any heterogeneous network environment you need to be really careful about what happens then you have new protocols like this interacting for shared resources. There are even TCP congestion control algorithms that aren't mutually compatible (e.g. under congestion situations one algorithm will be more aggressive and dominate the available bandwidth).