I define 'actual engineering' as in sitting down and desiging something, ie 'using CAD' as you state. There are R&D spots open for EDOs but if someone is joining the Navy as an EDO and expects to be designing, for example, the next DDG as a LTJG, he's going to be in for a rude awakening. As with any community, there are more options down-range but I don't necessarily think it's sound to make career decisions based on what you could do if you commit to the Navy for a long time. Something to keep in mind, yes, but the closest alligator is the JO experience and that's all that someone who 'just wants to repay the 4 years he promised' is going to get. For an EDO, my understanding is that entails the following:
-Get warfare pin
-Go to NPS or MIT (this would apparently be a 3rd master's for OP)
-SY or SPAWAR assignment to do EDO quals, vast majority of assignments are SY.