Fibre is not required to beat the 2.5Gb/s limit. Standard copper Cat 6a cables already support 10Gb/s for distances up to 100m.

If people have 6A and you use a large amount more power. For an application like a hard drive the power consumption of the ethernet connection would be more than the rest of the system probably.

So use twinax.

Which goes back to "non standard cabling is likely to remain expensive for quite some time".