My gut says no for two reasons.
Harmonious Mage says:
"Select two opposition schools. These are no longer opposition schools for you, preparing spells from one of these schools now only requires one spell slot of the appropriate level instead of two, and you no longer take the –4 Spellcraft penalty for crafting items from an opposition school."
Thassilonian Specialist says:
"A Thassilonian Specialist does not get to customize his choice for opposition schools — his opposition schools are determined for him when he chooses his specialization. These restrictions are more significant than those most wizards follow, and are known as prohibited schools. A Thassilonian Specialist can never prepare a spell that is in one of his prohibited schools — he treats these spells as if they were not on the wizard spell list. If using a spell trigger or spell completion item to cast a spell from one of his prohibited schools, he must use the Use Magic Device skill to do so."
Reason #1: Harmonious Mage is clear about what restrictions it lifts. You can use one spell slot instead of two and you don't have the -4 penalty to Spellcraft. However, not only does Thassilonian Specialist not have these restrictions (thus you can't remove them with Harmonious Mage), it also includes the note that your prohibited spells are treated as if they were not on your spell list at all. This is not a restriction that Harmonious Mage handles at all, so even if the schools were no longer opposition schools, you wouldn't have any of the spells to prepare because they aren't considered to be on your spell list. This is a dodgy reason, however, because it also says that the two schools are no longer opposition schools, so you could lump it all under the one umbrella. However, there's also reason #2, below.
Reason #2: While it may be verbal semantics, Thassilonian Specialists don't have opposition schools, they have prohibited schools. It's a very fine line, but in the interests of that and of the flavour of Thassilonian Specialist, I wouldn't allow Harmonious Mage to get around that limitation.
Quote:
Alderpash (First Runelord of Wrath), still has his head as WotR 5, Instead if it decorating the weapon of Alzanist. (Shattered Star 6).
That question was posed to James Jacobs. He seemed delighted that somebody had noticed, but elected not to explain further.
I think I had a Sorshen build kicking around somewhere that was half-done. Might have to dig it up.
