If you've used rat turds then you're familiar with the Vomit rat, the warrior rat, the rat arcanist, so on, so forth. Maybe you've even found some cheese (OH GOD THE SPOILERS) and summoned a few yourself.

But why can't you use the items that summon rats to actually summon rats? My suggestion is this: allow the use of -some- items that summon from a certain theme to be used as reagents of that theme.

Example: You find rat turds, they summon creature II one time. You used the conjurative focus on them and you can then use a summon spell to summon creature III and get a rat arcanist, thus consuming the rat turds in the process.

I swear to god this is a serious suggestion and not merely an excuse to use the phrase "consuming the rat turds".