If your goal is to be a Nuc Officer, you should probably ask for EM or ET as that will get you plenty of time in the "box" (if you make it to prototype before hopefully getting picked up) and coordinating events in the box is the largest hurdle new officer students seem to stumble over. If you can't coordinate things in there how will you ever have your thumb on the pulse of the entire engineroom and run it safely and efficiently? By going ET or EM once you get to prototype you'll have some exposure to how things run in there and learn many of the conventions that a young officer should know without even thinking, that they often get hung up on.
If you go STA-21 you MUST be commisioned in the unrestricted line, it's a requirement of the program. Only after commisioning will you be able to apply for a restricted field (Nurse, Medical, Engineering LDO -ie. Naval Reactors, Supply, maybe a few more but those are the biggest). Restricted officers will never command a warship and don't fit your typical "officer" bill but due to their expertise and training qualify for officer pay. Imagine trying to pay a doctor enlisted pay!
However a doctor will never lead troops/sailors/marines into combat.
Starting from boot camp volunteer for every leadership position you possibly can, one usually begets another. For instance, RCPO (highest leadership position available to recruits in boot camp, for Navy) will have a very easy time being designated Class Leader in "A" school and thus much easier getting class leader in NPS and thus easier getting Class Leader in Prototype, and when you put your package together, you have a long list of leadership experience to set you apart from the thousands of other applicants, and is even more important because as a student you won't have any fleet performance record to fall back on. Demonstrated Leadership POTENTIAL is what they look for, and the motivation to follow through with the STA-21 commitment.
If you have any questions email me at canty.13@osu.edu,
Respectfully,
OC Russell Canty
(MM2 ELT instructor on MTS-626 Charleston Prototype, Crew "E", selected for STA-21 starting school Fall 2003)