In truth, the phonology is unimportant for making a loglang. For making an artlang or an auxlang (auxillary language), phonology is very important—but not for loglangs. It’s more of an aesthetic choice. Also, I’m not very good at phonology. I used to have a loglang partner who co-created the language with me, but she left early on because of mental health issues.
Conlang making is weird because it’s less “design” and more like...feeling what feels right. There are certain things that seem correct and certain things that feel wrong based on which elements you’ve put down previously. You “fix” some points, and the rest of the design falls into place. In that sense, it’s more like discovery. I’ll tell you a little history about Sekko’s phonology, though.
Sekko originally had a Finnish-esque phonology. Voicing distinction on plosives and affricates (we had tʃ dʒ), no voicing distinction on fricatives. At that time, we also had the labiodental fricative f. Vowel and consonant length distinction were already present. The approximants j w were treated as separate consonants and not treated as diphthong allophones—diphthongs were instead pronounced with hiatus. The palatal nasal ɲ was also a separate consonant and not an allophone.
There was no voicing distinction on fricatives because we didn’t want a v-w distinction (and because Finnish didn’t have it either, but we soon stopped caring about faithfulness to a Finnish-esque phonology. Now it’s more of a weird mix of Japanese and Mandarin because of the labialization and palatization of consonants).
Now, this was all fine, except that I didn’t like how diphthongs had to be pronounced with hiatus. It’s much better to permit them to be said with glides. That entailed removing j w as true consonants.
I didn’t like that we had no ʒ but we had dʒ. The labial fricative was removed, and voicing distinction for fricatives permitted.
Because consonants can be palatized now, we had a tj tʃ distinction (think of English “tube”). I didn’t like this, so the affricates also lost their status as true consonants and became allophones.
Now there was less reason to remove ʃ and ʒ (I actually might re-add them). It’s the same situation as before, where there was a sj ʃ ʃj distinction. I didn’t like that very much, so the post-alveolar fricatives had to go.
In truth, the phonology is unimportant for making a loglang. For making an artlang or an auxlang (auxillary language), phonology is very important—but not for loglangs. It’s more of an aesthetic choice.
I don’t see any reason to think of strict categories like auxlang and loglang that are mutually exclusive.
The notion of a loglang means that you want your language to fulfill certain criteria and are thus willing to make it a bit harder to learn, but that doesn’t mean that ease of learning the language is irrelevant.
Lojban itself goes through exercises like making it’s terms resemble existing words to be easier to learn.