Well, I know about C166/167, but while it is probably cheap (used in considerate amount of ECUs, and many Siemens products) it is not exactly readily available.

Well, I know about C166/167, but while it is probably cheap (used in considerate amount of ECUs, and many Siemens products) it is not exactly readily available. Also this architecture is, to put it simply, weird, I would describe it as 16bit hybrid of MCS-51 and Alpha.