Finally, we have a guess at the question of how many Heavy Weapons can you have in a Crusader Squad, by Neophyte Bob in the comments of the RAW vs. RAI article (two below this one). And he is right...mostly.
The mostly part is that if you take multiple Heavy Weapons on a guy the first thing your opponent is going to say is, "Cheater!", or something along those lines. Of course, you can point it out to him, but unless he is one of those who follow RAW closely, he probably isn't going to go along with it. On top of that, even though it is strictly allowed (as per poor-wording), it isn't very sportsman-like. It's kind of a gimmicky thing that could prove useful but is neither necessary nor friendly unless your opponent thinks that it is neat to have that option.
However he did nail all of the things I was looking for, though I would like to add two things. The first is that you can only fire one at a time, as per the main rules pg. 15 (you have no idea how hard it was to find that sentence that I knew was in there). So even though you may equip an Initiate with both a Lascannon and a Missile Launcher, he cannot fire both at a Rhino at the same time. However, what you can do is equip a model with a Multi-Melta (for great short-ranged Anti-Tank) and either a Lascannon (mid- to long-range Anti-Tank in a Shooty squad) or a Powerfist/Power Weapon (for an Assaulty squad). But again, unless you've got a casual opponent to play with (because I consider this to be one of those things you do in casual play, because then things are looser) who likes the idea of it, you probably shouldn't in practice.
On a different note, I have just recently joined the From The Warp blogger group, hoping that I might get some more readers and perhaps have some discussion in the comments once in a while (between more than just three of us). There should be the FTW image somewhere on the right before too long, and hopefully we'll get some more traffic through here.