Agree with tacklebox on suspension tweaks. A la MBA, it'd be cool to see a suspension mod: shootout on a stock bike between the suspension tuner's in Van and Whistler… to see what they'd do different to customise and optimise. SuspensionWerx, Vorsprung, Susp Therapy.
It'd be cool to see what makes a bigger difference on a stock bike - custom suspension tune, or just properly setup stock suspension.
I'd also like to see a bike test across a model to see how much of a diff componentry REALLY makes. IE - take a top-end Enduro and a bottom end Enduro back to back. Then we can see where our money should be spent, assuming the frame design and geo remains the same.
I also think cable ferrule testing would be riveting.