Strategy for safe spoke removal Let's say someone had a heavy, overly strong front wheel on their re-purposed mtb. 26" wheel, 36 spokes.

What would be a safe pattern to follow to remove between 6 and 12 spokes?
To weaken the wheel you really want to remove a multiple of 4 spokes, so you balance leading, trailing, left and right. Six would be tricky. If the rim is reasonably strong you should be able to remove 12 as 3 groups of four to give that Shimano-style gapped spoke pattern. You'll have a gap, obviously, but the wheel will still be somewhat evenly tensioned.

Ideally you'd rebuild the wheel with the missing spokes distributed as a missing pair from every 6 spoke positions, but that would probably be more work than you want to do. If the wheel isn't fairly new the chance of stuck spokes is high, and disturbing it makes it more likely you'll damage something.

If you're reasonably familiar with truing wheels I suggest backing everything off a turn, removing the spokes, then tightening it all up again. That will let you work the spokes into a reasonably even tension while keeping the wheel straight. Removing groups of spokes when everything is tight will cause odd stressing mid-process and the risk of pulling a nipple through the rim or taco'ing are higher.

But... you're only going to save 20-30 grams, when a lighter wheel will save more. I'd stick with the strong wheel and save/scrounge a light one.

Also, per the comments from Criggie and Daniel R Hicks, if you are cutting spokes remember that they are under tension and the cut parts can exit the wheel with some force. If you want to keep the wheel it's better to back the spokes off rather than cutting them when tight.