In situations where the wording is unclear - which is always going to occur, because English is an unclear language - then you have to ask what is the purpose of the rule? And the purpose of all D&D rules is to make the game fun.
Trying to pedantically parse the exact wording, when the person who wrote it clearly didn't consider it important, does not make the game fun. Extending that kind of thinking on a wider scale is why lawyers get paid such ridiculous amounts of money, and we still don't get any justice.
The issue is that new DMs who aren't yet happy houseruling, and situations like Adventurer's League, where the rules must be followed consistently, require you to parse and abide by the
exact wording.
To be blunt: The rules should be written so that they work as written. A rule that doesn't work unless interpreted by a reasonable DM should be written with that interpretation
as the rule.
Just out of curiosity, what spells would you suggest that an Alchemist and Cartographer put into the SSI?
Battlesmith gets Conjure Barrage. Armorer and Reanimator get Lightning Bolt. Artilerist gets Fireball. Do you consider an upcast Cure Wounds spell to be better than those three spells some subclasses already get? Or are you just opposed to 10 rounds of 6d8 healing?
The Mark of Making feat gives you Conjure Barrage as an Artificer spell, so do you consider that to be a problematic option for the Artificer?
I am interested in this as well. - Although because a lot of my characters are AL, I think that selecting an upcast spell won't be an option, and neither will Dragonmarks in most cases.
In general, concentration spells aren't ideal for SSI because of its nature to repeatedly cast the same spell. However there is the option of using SSI with a concentration spell, and passing it around your party members or minions, with each using it on a subsequent turn. This will build in power as the fight progresses but might only be effective for large, long fights. I'll call that Cumulative casting and consider it separately. Many party members may have other things to do with their actions so it relies on having lots on minions.
From Base list: Aid might be better than Cure Wounds for healing in and out of combat.
Web with a better save than a Wand of Web?
Catapult spell if you've been mass-producing Acid flasks with the Alchemy jug?
Out of the adventuring day, you could use it to give all of the party a Homunculus Servant each.
Cumulative: Haste is an option, but a risky one. Heat Metal could be another option.
Alchemist: Acid Arrow isn't ideal since you won't get the bonus damage.
Either Aid, or Web, from the base list is probably best. Homunculus or other minion casting web, or Catapult with an oil flask, then you follow up with Firebolt could be the go-to.
Cumulative: Producing an additional Flaming Sphere every round could make a battlefield very hazardous to your opponents.
Cartographer: Bad.
Guiding Bolt might be your best option.
Cumulative: Call Lightning's 10-minute duration might allow you to set it up by precasting with a minion army before entering combat, where a spell with only a minute duration wouldn't be feasible.
