First, whoever played and RPed as a Red Wizard know the strain of people always hating you, and sometimes spending hours without significant RP all due to the nation and the class background. It's been allowed to make a lot of Slaves escaped from Thay while making unaccurate lore statement about the slavery and the nation.
Thay does not keep Elvish slaves as they are too chaotic of nature and constitution weak for harsh work in mines.
They also do not experiment on any plane touched people (Aasimars, Tieflings and all genasis) because in Thay, They judge them by their human side.
It's been allowed to be going on for years and making RW even harder to play.
I would like to propose to either remove the extra forbidden school or just follow the FR lore about "when to take the levels". When I created my Red Wizard, the DM team removed the "Take first level at lvl 6" rule to ease the burden of being a Red Wizard. Taking the level at 17 makes it viable. It is possible to get most spell from your new school,but after your first level you lose access to learning new spells, keeping those already known. All I'm showing and explaining here, it is Lore accurate. (paraphrasing, will edit when i find the lore part from the book) 'Many wizards takes on the REd Wizard path late in their career, in order to keep access to certain spells."
Also, the very, very...VERY useless Circle magic. I tested it, back when there was more than 2 red Wizards around. I was lvl 30, and the one assisting me was level... 14 or 15. Circle magic is suposed to empower the circle leader and make his magic stronger. The way the math was done on the ability actualy made it weaken my lvl 30 Spell caster. In order to make it work fine, i was told "Be 4-5 and all powerful or it will weaken the circle leader." which is unrealistic and inaccurate representation of the ability from PnP.
Uncapping certain spells would also help! (but I'm dreaming I know