One fascinating aspect of Hakhel is a mitzva to bring gerim. Bringing children is often discussed, but gerim? I apologize that I do not remember the source for the below (my thoughts are in []).
Are these converts? Then, they are already included into previous groups. Then, it means (righteous?) non-Jews who lived among us. Is it a mitzva for them? It can’t be – they have 7 mitzvos and this one does not seem to fit into any, so this could not be the 8th …. [AAQ: furthermore, mitzvos bnei Noach seem to be universal, they do not presume that they need to live in traveling distance from Yerushalaim]. Then, it means it is a mitzva for us to bring gerim to Hakhel. Can we order them? [AAQ: Beis din arresting Palestinians and taking them to Har Habayis?]. This can’t be also. Thus, the conclusion is that we should behave in such a way that gerim would want to join us.
[AAQ: Sounds a little bit like proselytizing, but it is once in 7 years, not a daily thing and corresponds to R Salanter’s approach (I don’t think he meant non-Jews though) – one should always argue for Yiddishkeit – sometimes even with words ..]
[AAQ: an alternative explanation: mitzva for non-Jews to establish a system of justice would make it reasonable to them to go to Hakhel to learn about it. This may be complimentary to the main argument – we encourage them because they need it. Of course, when they come to Hakhel, they will hopefully see and hear things that will help them to improve their understanding of justice.]
[AAQ: so presence of a large nuber of praying non-Jews on Har Habayit is legit at least once in 7 years. We just need to put loud speakers to make sure Torah reading is louder to whatever hate speech they have there]