It's a good poser for sure. Had the PCE never aspired to have the CD ROM, were it not the first console to attempt that, it would definitely have needed to up its game to compete with its rivals, who generally were developing more hi spec hardware (though nowhere near as good LOL!). It's known that the Supergrafx bombed due to a mismatch between what was only a slightly better PCE, and customer expectations from the 16 Bit generation. And it's clear that from the very beginning of the NEC project, the CDROM was on the cards. What NEC would have needed to do, without the CDROM, is develop something akin to the Supergrafx but with yet more processing power. Something above a Megadrive but not quite at N64 level.
As it was the CDROM held the PCE in very good shape despite a fairly low share of the global market.
Generally the extra RAM etc that made some CDROM games more impressive than their HuCrad forebaerers (Spriggan, Sylphia, and of course Sapphire) might have been , as was suggested above, incorporated as a hardware or JuCard add-on (SFII). The PCE was always designed with peripherals and expandability (check that huge ext bus!) in mind, so who knows what sort of add-ons could have been developed? As it was, the CDROM was shrewd. It provided the earliest console foray into CD sound, extra memory and that progressive leap into new technology, which always inspires people.
The HuCard, both aesthetically and in performance terms, was an incredible medium though, and remains in my view the ultimate gaming medium, taking cost, size, reliability, looks, performance etc into account.