What do you think the furthest extent a lesser spren can develop is?

[Grimn]

I was thinking of artifabrians and different ways they could use spren, taking inspiration from the little trained flamespren bippy, and other humanoid lesser spren like windspren. Spren are shaped by thoughts, and from what I've read on coppermind and the rpg, copper in fabrials can be used to transmit thoughts while bronze can increase a sprens capacity to recieve thoughts. Say you rigged a fabrial with a bronze and copper cage covering a gem with a spren inside, you could theoretically turbocharge the "training" or personifying process.

Do you think that could work? and if so, do you think lesser spren are capped out "Sir!" and animal intelligence, or could potentially develop further?

[Nitpicking]

We know that windspren can be "raised" by an Honorspren (or the Stormfather) to become Honorspren themselves. I've assumed (but have no canon evidence) that the other truespren have similar origins.