Apart from the PSUs which were to a specific design, what other components are bespoke? And it is not something I would worry about.
Yes the cases might be as will some mounting hardware but that happens with EVERY manufacturer.
The worst one is proprietary motherboard
Presumably graphics will be onboard so if there is limited space for a replacement graphics card repairs / upgrades could be expensive.
Ex <n>ildram , been to SKY MAX - 15,225 Download
BE Unlimited - 21,000 Download 1,200 Upload,
Moved house, now BE Unlimited 6,500 Down, 1Mb/s up - gutted!
FTTC Cab installation commenced 12th April - expect full 80 / 20 - bye bye BE, hello BT Infinity soon!