I definitely agree in principle, but I don't think it's realistic.
Toyota hasn't developed a turbo straight-6 in over 2 decades (JZ platform). They made that financially sustainable by also putting the engine in higher volume cars such as the Lexus IS300, GS300, SC300, and overseas models like the Mark II. I feel that the turbo straight-6 in a balanced RWD platform is crucial to it being a true Supra in my eyes, and most of the 6 cylinders in the Toyota/Lexus lineups are NA V6's, and headed towards hybrid variants. BMW is arguably the best manufacturer of the turbo straight-6 in the modern era, and no slouch in building RWD cars with great handling. Many millions saved right there in R&D = a lower price for the buyer. I'm not even sure the added cost in Toyota R&D would result in a better sports car overall.
Sports cars just aren't profitable, and their development typically have to be subsidized by either collaborations or shared platforms/parts. Otherwise, they're developed from the ground up and thus charge the premium for it. Hence the GT-R and NSX moved upmarket to $120k+, and most people who say they wish the Supra competed with them would never buy it. Many more people can afford the A90 Supra. To be frank, at GT-R and NSX money, I'd get a new 992 911 C4S or GT3.
If you want to look at complete Toyota (Lexus) sports car creations, look at the RC-F, GS-F, LC500, IS-F, etc. While their NA V8's sound amazing, nearly all of these models were understeering boats way behind the performance figures of their competition, while charging similar premiums.
The Supra on the other hand has a fairly robust and powerful turbo straight-6 and is priced $15-30k less than its rivals such as the Porsche Cayman S, BMW M2, and Jaguar F-Type R-Dynamic. It performs amazingly and has held up on the performance end, and drives like a pure sports car compared to the "somewhat sporty" cars Toyota has made over the last 20 years. Heck Toyota barely even has Apple CarPlay and user-friendly infotainment figured out, not to mention the luxury appointments and balanced RWD chassis that BMW has figured out also.
I certainly wish Toyota could develop it and the 86 entirely on their own, but it's a different era of cars entirely.