I agree that to make work the ISO part is the first goal, the hardware is here, an Arduino and the "free" MC33290.
For CAN you need conformance and qualification, so you have to use either the ELM327 or the AT90CAN. The atmel CAN exist only in a "thin quad flat pack" like you said and unfortunatly there is no arduino like dev board for it.
I really don't know... ATMega168+LCD+ELM327+parts would cost about $60 for sure. If we take the AT90CAN way, we have to design our own board and still use externals MC33290 and MC33390 + some parts etc. It should cost less except for the board/PCB.
I didn't want to use the Arduino for iso/vpw *and* the at90can for CAN, the solution is to use either the arduino+ELM327for all protocols, *or* the at90can for all protocols, not a mix
