From what the Hornby Mag video said, this system seems to be very well thought out.
The decoders have a socket on them for attaching back up power - 9s worth I think. Note that's a socket and not some teeny weeny solder pads and the back up power pack is keenly priced. So that should address dead spots on the track. An additional advantage is that this is powering the decoder so the Bluetooth is still alive and you can control the loco.
There's a 'Legacy' (cheeky name

) dongle which will connect the Bluetooth system into an existing system. The publicity material shows a Z21 as one potential target. I just had a look at the product page -
R7326 HM7040 - Legacy Dongle for existing DCC Controllers which tells very little but I did follow the link to
https://d63oxfkn1m8sf.cloudfront.ne..._HM7000_Incompatible_Device_List_9-1-2023.pdf and noticed that my two year old Samsung phone is there alongside a lot of other Android devices. That's going to be a big blocker - not everyone has an Apple device.
Metal bodies - The new HD models have the socket in the tender and that's plastic? For that reason? Doubt it but ...
I think the emphasis from Hornby is that this is a cheap way to get into digital control. My guess is that Bluetooth is built in to just about every chip you might consider using for a decoder so it's effectively free. They've designed the power provision so that you can reuse an old Hornby wall wart. So your entry cost could be as low as a decoder and power adapter lead, just add a compatible phone and you are in business. No command centre costing hundreds of pounds.
For people starting out, or who only have a few locos it's a nice low cost entry point, and as the decoders can accept DCC signals via the rails, your investment is protected should you visit an NMRA DCC layout at a friends or a club or even upgrade yourself to a full system later.
But it's nowhere near a full system such as those from ESU, Roco and others. Just look at all the accessory decoders and detectors to get an idea of what's not there. It's pure loco control at the moment.
There is a full article on Key Model World but it's behind there paywall and Hornby Mag subscribers no longer get free access. Maybe it will be in the Feb edition but mine's not arrived yet.
David