If one has a wheel like this (excuse my crude drawing).

MissingSpokeWheel.jpg

Deletes the dashed spokes.

Then the two red spokes at the bottom will increase in tension due to being the only spokes that compensate for the black spokes on top.

The tension of the black spokes will likely decrease slightly (fewer spokes pulling on them).

One might expect the wheel to naturally taco somewhat, which I presume would also decrease tension. However, if one deletes the spokes symmetrically, then in theory, one could have a moderately true wheel that would remain.

Oh, I could also imagine field-truing a wheel that just lost half the spokes in a crash