We're quite aware of Michli, but what you'll notice very quickly is that all the writers of the books have been members on AN who have consistently been able to explain concepts clearly to a broad range of students through help in threads and PMs.
From a marketing perspective, yeah, there might be a marginal difference between Thushan and Michli, but in reality it's not going to convert as well.
Derrick Ha's particular success, is because he was incredibly involved with his school, an extremely effective communicator, very modest, and good at a broad variety of things. In all honesty, kids who get 99.95 easily fade away from the limelight within a few years because quite frankly a lot of them don't do much interesting with themselves (from my perspective). Derrick Ha began creating value for the VCE community the moment he left, and did so in a massive way with his lectures and notes, and Thushan has been following this quite successfully and has definitely already made very valuable contributions to the VCE Community with his questions, lectures, and forum assistance. We're more than happy to look into more candidates (as we will with Michael), but I'd ask you to see our writers as more than just marketing tools, because they're actually freaking amazing at what they're doing.