Visual appearance:
The glamour aspect of relics is one of the parts that was least harmed by 4.0. Like before, there are effectively 3 base glamours, with special glow effects being added in later stages. However, it is notable that 2.0/3.0 had very personalized effects for each weapon, whereas the general shape and glows available in Eureka are not significantly different for each class, which cheapens the "special item" feel that relics typically have.

Level skip:
The level skip in 3.0 was actually a very nice touch to make it seem like there was a contiguous story between the relics. SE has expressed some concern about the time skip, but as someone who did ALL the 2.0/3.0 relics, and therefore had to do the first portion 3 times, it wasn't significant of a time-saver. This would be a good idea to bring back for 5.0 (but again, keep the skip content short).