Re: what 7 string would best replace a ibanez universe?
The 7620 and 1527 are very similar spec-wise, but have very different neck carves. The 7620 is a little more C-shaped, though not quite so much as the older UVs, while the 1527 is more of a D with thicker shoulders, and to me felt a lot more like the newer Universes I've played. I THINK they're the same thickness as each other, but don't quote me on that.
Which you prefer is personal preference - to me, I definitely preferred the 1527 carve. It seems like the same carve as the 2027 and CST (I've all three, just never at the same time, so there's a little bit of memory involved here), and it's my favorite of the Ibanez 7-string neck profiles.
If you've played the older UV neck carve though and really liked that, you might be better off with a 7620.