Already 15 months into my part time MPhil/PhD. Trying hard to cope both side for being a full time engineer and a part time student.

Research field in engineering.
Topic: Energy harvester for thermoacoustic engine.

I beg to differ.

Taking PhD =/= academic line is the only way out. PhD is not just a cert, but an intense 3 years training that is much gruesome than working experience itself. It teaches you the quality of a real engineer. Project management, design for experiment, analytical technique, critical thinking, problem solving skills, paperworks, social skills etc.
Once you graduated and enter industry, you can get into senior engineer or senior researcher/analysts in big companies. Most of my seniors that graduated worked in technical field in GGS, Abbott, Dyson, GE and Lockheed. So, your statement is not true already in these days.