I don't have a strong opinion on letter usage, but I'd like to point out that not using all letters is really, really not necessarily ignoring or mocking anyone.
I use "LGBT" even if none of these letters correspond to my own situation. I'm neither ignoring nor mocking myself, I just use the form that most people know best, including outside of the community, and the form that is the shortest. Not everything has to be literal. LGBTQIA+ is also incomplete, unless we take in account the +, but then... LGBT+ works too! (I need to get into the habit to put the +, I'm not used to, but I see the point and it's not much longer).
Now in this case. LGBTQ+ is indeed not a good compromise in my opinion. The including of the Q may make people upset to not been included, in a way they may not have felt if the more classical LGBT+ was used (?)