I noticed a shiur being delivered tisha bav afternoon on the Rambam's laws of the Messianic King. This is interesting. Torah study is usually prohibited on tisha bav. Does this practice have a source in Jewish tradition?
Rav Qafih writes in his commentary to Hilkhot Taaniot 5:11 that the custom of Yemenites is to read passages relating to redemption. Rather than cheering one up, they emphasise by contrast our current plight, which evokes the proper feeling for the day. It could certainly be argued that this is similar. (Although admittedly not all the halakhot necessarily imply positive things that we are currently lacking, but it would certainly be a highly related precedent.)