Comment 10 for bug 895223

Wow, I really vote for this!

Not the bollocks with unit upgrades, but just a simple prerequisite satisfier.

But I'd implement it like this:
[ANYUNIT]
IsResearch=yes ;this would work on any unit type. On construction complete, the unit would never actually appear (or the building would not require placement) but the owner would still satisfy the prerequisite ANYUNIT (even though they don't actually have an instance of it)
Can also set BuildLimit=-1 so that ANYUNIT would disappear once complete.