Phrases

Instead of aiming for sentences, maybe go for words and modifiers that form little fragments, which you could manually chain together to express things. So for a noun, if you do a long press on the tile you would get a window of modifiers which would be adjectives (mostly) and a verb you could long press to get sensible adverbs or modifiers that go with the verb. This could go beyond adverbs and change to related concepts, so you might do a long press of "walk" and get "run", "jump", "Cycle" as well as "quickly" and "Slowly". These should be designed in such a way that it preserves the part of speech, so a noun plus modifiers is some kind of noun phrase that can be slotted into the same sentence structure as the root noun. "I want the ball" and "I want the (big red bouncy ball)" would be an example of a noun phrase replacing the noun.