Generation and structure are important, but IME IDs arent complete without consideration of representation; encoding and opacity.

* User facing IDs must be opaque. If users can infer any structure or ordering from your ID they _will_ use and they _will_ create awkward dependencies on "your" implementation detail. My favorite example is the multi year and many many dev years of effort that went in to extending EC2 instance IDs. They were already assumed/intended to be opaque until clever users inferred the structure! The simplest answer of something like block cipher is so cheap as to be free (and can be accounted for as part of versioning).

* Encoding should be tailored for teh primary UX. Ex teh base32 variants are reasonably efficient and accommodating of text selection & input. Dictionary schemes (ala S/KEY rfc2289 or BIP39) may be more appropriate for voice communication.

* Following ID structure -> opacity -> encoding you should probably account for the block size and encoding efficiency to minimize padding or excess characters