I totally agree. ;)
That's why I suggested 0-1 everything except troops. Your at the bottom of the slope, and it's "fair" to each army.
It doesn't solve everything, and there are other problems with it, but I'm still working on it ;)
Restricting any unit for a game like 40K doesn't work because, unlike something like MTG, you have a very limited amount of resources to make an army out of. Restricting cards in MTG doesn't mean asmuch because there are thousands of cards you can still construct a deck from, in 40K and FB you a limited to the 20 or so units presented in the codex. Restricting that one unit could hurt your codex quite a bit.
Units are "balanced" (a loose term in this case) based off the rules presented in the codex. To modify those rules reduces the effectiveness of said units to the point where they may not really be worth it to even play.
Think about it. A trio of Heldrakes are a badass team that will ruin another players day. Making a rule that the player can only take one makes his Heldrake a much bigger risk, as it will still be a huge target but can't produce the same results without it's team. The question then becomes is it worth the points or am I better off running an additional unit of X.