Here's a quick and dirty fix for checking for elixirs as well as flasks.
In the BigBrother.lua file, there's a variable which contains a list of buffs for the flaskcheck functionality. It's near the beginning of the file, so it's pretty easy to find. You can just add the buffs you want to check to that list in the same format if you want to use it to check for elixirs as well. You just need to be careful to get the name of the buff as it appears on the character (Major Agility for Elixir of Major Agility, for example).
This is what we use, and while it doesn't ensure that everyone is using two elixirs, it does tell us what Battle Elixirs they're using.
local buffs = {
"Flask of Arcane Fortification",
"Chromatic Resistance",
"Distilled Wisdom",
"Flask of Fortification",
"Flask of Mighty Restoration",
"Flask of Relentless Assault",
"Flask of Shadow Fortification",
"Supreme Power",
"Flask of the Titans",
"Supreme Power of Shattrath",
"Fortification of Shattrath",
"Mighty Restoration of Shattrath",
"Relentless Assault of Shattrath",
"Major Agility",
"Major Shadow Power",
"Major Firepower",
"Major Frost Power",
"Elixir of Mastery",
"Healing Power",
"Major Strength",
"Adept's Elixir",
"Onslaught Elixir",
}