Yeah, I think we should wait for the next turn before deciding what to do. Although I don't agree with your opposition to making another system.
From a quick retrospective, we're spending this whole turn reacting to Moskerg's introduction of widespread cavalry, which is a win for them because they're probably going to design something different in the upcoming turn, forcing us to react to that too ad infinitum. Note that Mossberg initially didn't have any weather magic at all (they started with Divination spellbook) and yet they went from making farts of wind to gales of wind to entire storms to calling down lightning on our plate-mail troops. In the process, they've pretty much abandoned further progress in Divination and mind-reading entirely. We need to be more like them and be unafraid to branch out, which should be easier for us as Conjuration is inherently about making new things.
While I don't think the hole spell is optimal (most people can jump over six feet with a running start, to say nothing of a horse), we should try exploring Conjuration further. Some ideas are:
-permanent conjurations, like the magic lances but improved. If successful, will be game-changing as we can have skilled mages producing them en masse in the capital, instead of as needed on the frontlines.
-bigger living things/animated constructs, such as the crystal spiders proposed earlier. Basically shifting our living conjurations from a harassment role to direct combat.