Let's look at this post in 2-3 years time.Look at the history. EMTBs primarilly designed as trail bikes and typically 150mm travel front and back were all about the same weight if ally..........maybe a little less if all carbon but not much. Then many of those trail oriented EMTBs ventured into the realms of Enduro which meant 160mm became more dominant with thicker stancion forks and piggy back shocks......at the same time batteries started getting bigger and heavier. Overall these bikes were much heavier duty.
All EMTB ally bikes are made from 6000 series ally ( Except the Polma), equipped with robust wheelsets and well protected tyre casings. So where are you going to lose a few Kgs without weakening the frame?? The same could be said for carbon framed bikes. Many of the frame elements have to withstand compression which is not the strong card for a lightweight composite construction.
Answer: smaller less powerful motor, smaller battery, XC quality wheels and tyres, carbon bars and cranks, maybe lighter suspension components.......or skimp on frame strength ( carbon or ally)..............all of which spells an XC or maybe a trail bike but not a bike park or enduro bike. To achieve ultra light weight with composite design the frame cannot be the same design as for an ally bike.........it needs a rethink.
The developments that would enable a full enduro design at a lighter weight would be the use of 7075 ally instead of 6061 ( but specialist welding techniques required), full capacity batteries that weight much less..........or maybe fuel cell rather than lithium, a complete redesign of the drivetrain; tyre technology that at least equals Maxxis DD type protection at half the weight. Caron frames with a very different desing to ally frames.
When all of that is achieved having a lower powered motor becomes irrelevant..........after all you can decide how much power you want/need already.