Can happen xbox one x to be able as series x? What demand be add software or hardware? Just...

We can't help with console modifications as it violates the Terms of Use & can lead to a console ban.

Lots of games from the Original Xbox are going to get the Backward Compatibility treatment on Xbox Series X (through hardware, not software). They just discontinued the BC support for this gen (they wont add any other games on One-One S-One X) but they
will on next gen. So just be patient and get your fingers crossed.

Other than that, maybe next generation they should consider some kind of harware bc approach instead of the current software emulation...

Hi.

This is already happening. The Series X|S is the same hardware architecture as the Xbox One. Which is why all Xbox One games work on the latest Series hardware. No software emulation.

It would just like to add that Series X|S games are developed to only use faster storage. Not only is this storage totally different to a mechanical hard drive, the way games are loaded is also different. In addition, the Xbox Series X|S hardware can leverage additional resources to load to games from internal SSD or external SSD's even faster, what Microsoft calls its Xbox 'Velocity Architecture'.

As previously stated, you're never going to be able load your Xbox Series X games from an external hard drive. They're just too slow.

completely incorrect, they have suspended BC while they concentrate on the series x, all the 360 and og games are run in an emulator wrap, it is all software not hardware, the series x will be no different, it will also use and emulator to run the games,
dont forget the series x is just a pc with an apu.