I would like a feature where I can practice the example sentences that I chose to learn by writing the 拼音 (pinyin) as I do with normal words.

Any plans on making this new feature for me? :)

Yes, we're planning on including that when we do the next version of the example sentence system. That will be a ways off, though.

Just seconding my interest in broader use of sentences in studying - maybe giving writing/pinyin exercises for sentences that include multiple words in your 'to study' list and knocking them out through there as opposed to single characters/words.