I can't say I can comment on the realism of the specified scheme of diminutive for nouns versus augmentative for adjectives for nouny adjectives (being both a rather inexperienced conlanger and a non-linguist), even though I personally would have made both act the same way (like with my adjectives in Proto-Søkkli, which are not merely verby but indeed are full-fledged verbs, albeit with some special derivational inflections).

Well, now that I think of it, it should be okay, especially if adjectives aren't very nouny (e.g. are nouny only in agreeing with nouns, e.g.).