The future proof is so hard, and the specifications for ovens and hobs don't help.
It is clear you can't supply an oven with a 100 amp supply, there is no internal fuse with most ovens, so the supply must auto disconnect with a fault, but not actually seen an upper limit on the supply with any installation instructions.
Often there is a lower limit, but the big problem is a fuse connection unit has a limit of 13 amp. Once 13 amp (3 kW) is exceeded you need a supply from a large unit, most people don't want something like this
View attachment 265408in there kitchen, in fact mothers house we did have a mini consumer unit in the kitchen, but that was because the house needed rewiring and my dad refused to have it done.
If we could buy a 16 amp fused connection unit it would be easy, but not freely available in the UK. So we look at tradition, and traditionally in the UK cookers are supplied with a 30 or 32 amp supply, and traditionally we have used twin cooker connection units, so be it two ovens, or a hob and an oven, to use a 32 amp supply to a twin cooker connection unit is the traditionally method.
However I have looked at the internal wiring on an oven, and it does not really seem man enough to handle 32 amp, we are really relying on under fault conditions there will be an earth fault and the RCD will auto disconnect.
Using 16 amp supplies to ovens seems better, however I would use 4 mm² or 6 mm² so it can be up-rated in the future, however for this to happen we need the paperwork to show the circuit was designed for a 32 amp supply, even if a 16 amp MCB or RCBO has been used.
Most installation certificates do give the cable size, but it also needs to give installation method and most of the installation certificates fail to give installation method, and also of course need to be sure that is the latest certificate.
I mislaid the certificates when I came to sell mothers house, in the end I did find them, but realised there was some overlap, kitchen was done, then the wet room, then full rewire and it was impossible from the paperwork to say what certificate covered what.
I know the original hob in my mothers house was an induction hob, and the wiring was installed with a 32 amp RCBO, but the induction hob raised questions as if suitable with mother pace maker, and also the display could not be seen at the angle of ones eyes to the hob when sitting in a wheel chair, so it was changed to a halogen domino hob which only needed a 16 amp supply, so the RCBO was changed to 16 amp. There was nothing on the paperwork to say this had happened, and if the new owners wanted to swap back to a 4 ring hob, their only way to find out would be to ask me or the installer.
We can assume when we see 6 mm² cable that we can fit a 32 amp RCBO, but it that good enough? For all we know the 6 mm² could be because the cable goes through thick insulation so reference method 103# so 23.5 amp limit. With 4 mm² a 17.5 amp limit and I have seen nothing on the installation certificated to say what the worst reference method is.
So it is only future proof if the installation certificate includes the installation method.