Thanks you truly do know your stuff, something that comes with experiences with many iem's.
I don't hear the mids of TF10 to be as recessed as most people here do. It has excellent bass with great attack, speed & punch along with good treble. But, fit is horrible for most people. Even though I have nothing to complain about fit and seal, I don't like how they stick out of my ears . I consider TF10 to be an out and out fun IEM - something I can enjoy once I have them in my ears. Not many people here consider them so (except may be clieOS, mvw2 and few others). But, mids and Vocals are not the strong areas for TF10. TF10 might sound a tad artificial with vocals, which is why I did not include it in my short list. But, if you are prepared to experiment with fit, by all means take a chance.
Would DBA-02 suit your requirement? I doubt it. The bass would seem deficient coming from Eterna for sure. It's sound stage is not as spacious either. When I think of DBA-02, I remember the treble. Coming from Eterna, it may be a handful to handle as I read that Eterna's treble is largely inoffensive on the ears.
Do I like it? Yes. It is one of the few fatigue free IEMs I have despite the fact that it's treble is not something suitable for my tastes. Another reason why I like the M2 is that I can listen at much lower volume than most other IEMs (through Clip+). So, even in noisy environments, it gives me plenty of headroom.
M2's bass is soft and smooth on the ears. The bass is fine with texture, quantity and details, but it lacks the extension and punch. ECCI PR401 does better in that regard. M2 fits your requirement of forward midrange with good bass. It's treble stays slightly recessed, inoffensive, devoid of much sparkle or extension, so it won't draw your attention much . Unless you are looking for something with better treble, M2 is a good choice. Otherwise, consider Xears TDIII. It has a lush, sweet, forward midrange which may not be as forward as M2, but slightly better overall when it comes to sound stage, balance and presentation.