This is perhaps a wild idea but just mentioning it in case it sparks an idea.
At the moment, HH is setup so that the sounds and the components are taught in order that over a period of about 2 years (I believe) a basic level of fluency will be reached (with fluency defined by reference to what’s required for the HSK levels).
I recently ordered a set of 300-400 flashcards made by a Taiwanese YouTuber - Let's Fall In Love With Traditional Chinese Characters! | Cecilia Chen - which are organised by radicals but which (I’m told) aim to concentrate on what’s required for tourist fluency (including, in particular, how to read a menu).
This got me thinking that once I’ve learnt all the HH sounds, it would be interesting if it’s possible to replace the HH curriculum (fluency defined by reference to what’s required for the HSK levels) with a user defined curriculum (such as, for example, a list of a few hundred characters required for menus, shopping etc). Based on that, the HH website would then generate dynamically a curriculum going forward based on (i) the components which I already know and the components which I need to learn and (ii) the characters I want to end up knowing. The user would be able to change the characters they want to learn and each time the curriculum would be dynamically updated.
Based on this, for example, I could start off as I am doing now but if I suddenly wanted to concentrate on a set of particular characters, then I could change the curriculum and the website would change what I’m taught going forward. This would mean that instead of taking a couple of years, it could be a much shorter period of time before fluency for the desired characters (e.g. for a holiday) would be reached.
Separate from the above idea, it would also be great if the website could say that - based on current settings and the percentage so far of characters which are correct in reviews - it will take X time before it’s estimated that they are all learnt. I’ve just started on the HH journey (less than 2 months in) and it would be motivating / interesting if the website can tell me that I still have X months left until estimated fluency in HSK level whatever! Learning the characters is a journey which takes years and rather than an unknown time in the future, it would for me at least motivate me even more to know that if I keep up doing what I’m doing, I’m estimated to reach the journey’s end by whatever date.