You can put the (already released) Spring Reverb in any slot. I don’t know for sure but I’d be amazed if they prevented this in other reverbs that are coming. I am using the spring before the amp block and really like it for certain sounds -they’ve done a really good job with it IMO.
I'm actually interested (nothing critical, it's completely in the "nice to have" category) in having the X slot at the end so I can use an external looper and skip all (mostly delay and reverb actually...) built-in effects. RC-30 has a crappy but somewhat usable metronome/drum function and an aux input for backing tracks.