I've been bothered by this for a while and have been a little hesitant to bring it up, but it feels like SMN really needs a way (an action, either reworked from a pre-existing one or completely new) to recharge arcanum (Summon Ruby Ifrit, Emerald Garuda, Topaz Titan) for situations where you don't want to go into your 2-minute demi-summon immediately.
Although casual gameplay doesn't have too much importance due to most instances' clear conditions are "get target(s) to 0% HP", I'll bring up the most recent alliance raid "Jeuno: The First Walk" as an example for this. How it goes is that you start off the instance with a trash pull. As a SMN, you do not have access to any of your arcanum at the start of the instance, but do have your Summon Solar Bahamut and your Ruin 3/Tri-Disaster. You don't want to use Solar Bahamut here as it'll push the weaker Bahamut/Phoenix into your 2-minute window for the upcoming boss fight (and if I remember correctly, it does re-align eventually somewhere in the instance but still). Once again, I understand that casual settings really do not matter at the end of the day but it does not feel great to have the majority of your job's action kit locked behind your demi-summons. I will admit that high-end players probably have more issues to be said with SMN than I do, but I really wish this to be considered at some point.

Also, I would also ask for consideration for SMN starting instances with full arcanum as well. I think it could possibly be helpful somewhere and wouldn't make the job feel so inflexible at times.