I'd design an x carriage with removable pkates so you can build one with either system and mount whatever is needed. You can then also add a plate with a laser diode or dremel attachment.
It also depends on the type of flexible filament. Tpc flex is stiff enough to be used (at least in 3mm form) but if the filament is more compressable it could fold back upon itself in the cold end drive and retraction would not be practical. Mine is about 60cm and has trouble getting good results with pressure advance compensation, even with pla or abs filament. I decided not to use it.
With a large build volume you'll need speed, which needs the moving parts to be stiff and low on mass.
A toolchanger could automate swapping direct drive and bowden. That:s something I'd want to add to my diy 3d printer.
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Kind regards
Imqqmi
NFAN CoreXY printer:
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reprap.org]