I’ve been thinking along the lines for years. The main hurdles are manufacturing a case (the tooling for moulds is really expensive) and the lack of a suitable keyboard (I wouldn’t know of any modern mechanism as suitable as the Alps SKFL switches used in the Kyocera portables. Details: https://deskthority.net/wiki/Alps_SKFL_series).
What may profit from improvements are certainly the screen (80 cols please, tilting, like the Olivetti M10 had it) and real cursor keys (like the NEC PC-8201 had it). Of course, we’d need a few extra keys for a modern system. (Because of this, it doesn’t make sense to just jam some modern parts into an old shell.)
It would be my favorite machine, but I can’t see it happen. (No marketing department of a capable manufacturer would come up with something even faintly related.)
There was a project for something similar a few years ago, but it didn’t go anywhere. (I think, there was a prototype, but the costs of small scale manufacturing were prohibitive.)