I think it is important to remember that the E-J we saw in season 3 of Enterprise
was from an alternate timeline. So any actually E-J that exists/existed (and I prefer to think that there was one) could look very different.
I do like the "Universe class" (the E-J's class) we saw...but just not as the Enterprise J. Because it's really just a furute version of the NX class, not of the later versions of Enterprise.
And it's possible that in the future they revive older general hull configurations, I mean, just look at how the Akira class has design elements of the "younger" NX class (in reality, of course, the Akira came first, and it's design was modified into the NX when the ship designers ran out of ideas or something.)
But as it bypasses the later style/lineage of the 1701 enterprises, I prefer something more like this design, as it sports the 2 hull configuration of the previous 1701 Enterprises - so maybe in the Prime timeline, we could get an E-J that looks more like this:
Of course, it's in reality just the Altair class (an earlier rejected Voyager design, I think) with a Universe-type saucer mounted on top:
I wouldn't want them to discard the Universe class type all together, but in my head I prefer to think of it as a having a similar relationship to the ship design on top, and the Miranda class has to the Constitution class, or the Nebula class has to the Galaxy class...
I would even include the Altair class, as a straight up combat ship, but without the need to keep dropping a huge saucer section every time it's about to go into battle. Sort of like if somebody built just a Galaxy class stardrive section for purposes of fighting the Borg and the Dominion..
My only issue with all these ships is that they look too flat, and most of those windows on the saucer section would actually be pointing straight up, so they'd be more like skylights than windows.
Maybe a higher resolution version of the ship would correct that problem, as I understand that the E-J used in Enterprise was created in a hurry, at a low rez.
I'm also wondering about it's size. Those low-detail windows and surface features give it the impression (to me) of being larger than it actually is supposed to be. Which is about this size...(and not the miles long it appears in my mind.)