It would be difficult to randomize slice and phrase independently, and perhaps paketti offers the advantage here.
I would do what you’re trying to accomplish in one of two ways. Either 1: make multiple phrases that have the desired Sxx commands written into the phrases, or 2: use multiple c-4 Sxx phrases and then write in (what was) the phrase note data into the pattern editor. Perhaps with the help of a tool such as New tool (3.4.3): Travel Through Phrases v1.2 build 052 (November 2023) Then I would use the phrase control doofer to set up randomization or midi control of desired phrase number.
Here is my Phrase control Doofer:
Phrase Control.xrdp (14.7 KB)
As you can see, it allows for optional and automatable phrase randomization within a selected range of phrases. Give it a whirl and see if it helps. If you have any questions about any of the above, shoot.