I absolutely agree with the physics of this, however from my point
of view I can get the whole insulation done in the next few weeks,
and at some point later in the year I can board over only a
relatively small portion of the loft,

If you are only boarding a small section, then just crosslaying some 200mm
beams and attaching the boards to these should be pretty easy and will only
compress the insulation by 50mm or so. I wouldn't use it for medium-heavy
storage though. The self weight of the floor will already be high with the
extra wood, and boarding that the ceiling joists were not designed to
handle.

Christian.