Just send the cheap foreign engineers home, the demand for real engineers is still very strong.
The problem lies not with foreigners but rather the needs of profession to maintain viability itself. Of all the major professional qualifications, Medicine, Law and Engineering, Engineers have the least exposure as a form of service, e.g. - working with patients and/or handling clients, and are heavily dependent of capital intensive nature of spending money to make more money (machinery, infrastructure, process).
So, for example, while a GP takes on the role of front line health care and the dispensing of pharmaceuticals and the lawyer provides services to ensure compliance to concurrent legislation, the Engineer's role does not have a similar exposure to the front line customer. Even if there was, it would be on a maintenance basis, i.e. - If nothing goes wrong, no one gives a hoot that the Engineers keep it running, but when something breaks down, blame is easily attributed to technical personnel.
Thus, an Engineer only gets valued when they are in a position to build multi-million/billion dollar projects, and even then, their time in the sun is but limited or at least till the project is handed over to the client.
And in Singapore, projects such as these are far and few due to the size of the country and population, therefore local engineers are bereft of such exposure, thus requiring experience from overseas to ensure that should such amounts of capital be invested, the most capable person is found to ensure the biggest bang for the buck.
So in summary, Singaporean Engineers are well and truly in the toughest profession with the least financial return.