Somewhere I read a story about a group of TI sales engineers in Britain who put together a much more "typical" micro-computer system using the 9940 or 9980 CPU. They, of course, lost out the the 99/4 design because of politics. Though to be fair, I've heard there was A LOT of confusion over the 99/4's requirements. It supposedly started as a video game console after the Atari VCS was released to great acclaim in '77. But by the time they released it they decided they wanted to compete with the personal computing trinity: Apple ][, TRS-80 and Commodore PET.
I think it was certainly possible for SOMEONE to have come up with a better design targeting the nascent PC market. Also remember the 99/4 was pretty cheap compared to "real" computers. A typical CP/M or Apple ][ machine would have cost somewhere around $2500-$3500 in 1979. The 99/4 was a "bargain" at $1150. You have to think a 9900-based system that had a front-panel, floppy disk, RS-232 interface like contemporary CP/M machines wouldn't have cost too much more than a CP/M device. It may be a scratch more expensive cause you would likely want a bit more memory than the 16k that was common in the Altair or IMSAI machines at the time.
Every now and again 99/8 prototype systems will surface on eBay and sell for THOUSANDS of dollars. I just saw a CC-40 Plus system go for about $3500. Alas, I can't really justify that many dollars for these old systems. When TI got out of the business, they had the 99/8 and CC-70 in development. Assuming they were able to sell them for a decent price, they couldn't have been as bad at the 99/4 and CC-40.
You're probably meaning the Belgian designed DAI computer that was developed for TI initially but was then refused in favor of the TI-99/4. From a corporate point of view it made sense as the DAI was architected around a Intel 8080A. TI-99/4 had the advantage of using much more exclusive TI parts (CPU, Video, sound, I/O, GROM, etc.).
It's a pity that the DAI then could not gain market shares as it was a very interesting and capable computer. It had graphic capabilities that only later 16 bit computer could reach (Amiga, ST), had a semi-compiled BASIC that was fast, even on the quite slow 2MHz 8080, it could use an arithmetic co-processor (AMD 9511), it also had genlock which allowed to mix TV signals with its graphics (long before Amiga), etc.
I think it was certainly possible for SOMEONE to have come up with a better design targeting the nascent PC market. Also remember the 99/4 was pretty cheap compared to "real" computers. A typical CP/M or Apple ][ machine would have cost somewhere around $2500-$3500 in 1979. The 99/4 was a "bargain" at $1150. You have to think a 9900-based system that had a front-panel, floppy disk, RS-232 interface like contemporary CP/M machines wouldn't have cost too much more than a CP/M device. It may be a scratch more expensive cause you would likely want a bit more memory than the 16k that was common in the Altair or IMSAI machines at the time.
Every now and again 99/8 prototype systems will surface on eBay and sell for THOUSANDS of dollars. I just saw a CC-40 Plus system go for about $3500. Alas, I can't really justify that many dollars for these old systems. When TI got out of the business, they had the 99/8 and CC-70 in development. Assuming they were able to sell them for a decent price, they couldn't have been as bad at the 99/4 and CC-40.