Don't worry about the process..
First of all- Congrats on changing careers. I did it a few years back (Engineering to Pilot), and it is straightforward. The water is fine here, the pay is low, but will eventually catch up. (FWIW- I'm in my late 40s as well, and did the switch-- with no issues).
You do need your CMEL, and as people have said here, just go straight to commercial- no need to do private level. Add on the CSEL down the road. Once you have that and roughly 25 hours multi you'll be very marketable. Also, make sure you have the other ATP min requirements (night flight, etc). This is the right time to do this, there is substantial movement coming in the next few years.
As for the folks saying that engineers can't adapt to the airline world-- they are 100% wrong. I'm not sure what your background in engineering is, but the FMS programming and VNAV are really not that difficult, and your engineering degree indicates that you can approach the learning in a systematic way. If you have experience in programming or using software, I think you will have no problem managing the systems. The only difficult part in general is the large amount of information to process in short order- the "drinking from the fire hose". This can be mitigated pretty easily by being proactive in your studying and staying ahead of the workload.
Please feel free to PM me- I can tell you more if you like and what to expect.
Mustang304