How do PLA, PETG, TPU, ABS and/or nylon work together in a single print? I have a dual-extruder printer with a separate heating element for each head, thus able to combine materials in a single print job even if they don't share a single temperature range.

Now the question: When (outside of using expensive dedicated support material or doing multicolor prints for aesthetic reasons) is this actually useful?

Of common printable filaments (PLA, PETG, TPU, ABS, nylon):


Do some of these materials work well (which is to say, substantially better than just doing a single-material print with same-material supports) as breakaway supports for others?
Can some of these materials be dissolved in household solvents that don't harm others?
Do some of these materials adhere to each other strongly enough (and have sufficiently similar profiles in how they shrink on cooling) to reliably generate finished pieces comprising of both? (Especially relevant for anything+TPU, where one might want to generate a design with some soft or rubbery components).
The answers are   


yes
yes
probably


Which is to say, if you only want to use MaterialNumberTwo for disposable supports, then you should be fine. Presumably the slicer software is material-aware and adjusts the feed so the layer heights are the same for both materials. BUTbe careful that the support material isn't higher-temp than the object material, or supports which start from the object rather than the bed may cause local melting or distortion when the first layer is deposited on the cooler-melt material. 

But if you want to try to intertwine two materials for the final product, then certainly bonding will be a major risk, as will shrinkage during cooling (not to mention the risk of melting the lower-temp material while depositing the higher-temp material on top of it!).  If at all possible I'd recommend printing such parts separately and fitting them together post-print.