Hi JM1,
if you set your flashcards module to "Test type" Self-graded and "Show" Audio, you can already do something similar. Pleco will play back the syllables to you, and you will have to recognize both the right tone and pinyin and, if desired, remember the Hanzi with it. You could also create a category with only single-character words for use as your test set, to make sure you don't get any clues from word combinations.
Shun