The formulas could be endless, and this could be a great way to bring some much needed support to the economy. I honestly like the bound to account idea, and believe there are ways to improve on this to actually make items worth something again. Instead of salvaging those useless legendary and rare items, why not bring back the cube for some formula action using certain legendary items combined with gems, along side other crafting materials to help possibly buff those items?(or add runes to the game once again) I wouldn't say make the odds as good as the new crafting items, but make it so that the quality has a chance to be much greater.
Once a legendary or rare is used in a formula roll, make it so the item is bound to the account, and no longer able to be used for another formula roll, then salvageable. This would give legendary items with less desirable stats some value, which could be turned into the greatest upgrade possible... Like I said the chances should not be as good as the new crafting system, but the reward should be greater if one is to strike gold. Actually I rather the items not be bind on account, I want to be able to make gold off some of the effort... Sorry I'm sleepy and still thinking this over in my mind.... You get the point..
There are many formula ideas that could be generated to bring life back to the economy, and there are so many possibilities once the cube is returned to its former glory! Diablo 3 is suppose to be an upgraded version of the Diablo series, that does not mean its suppose to be a completely new and different game. Some things shouldn't be changed or removed, especially if its not broke. The cube needs to make its return sooner than later, I don't want to wait till an expansion...
Sorry for grammar issues, I just leaped out of bed to post this, and refuse to proof read...
Now for the memory of some old D2 cube action !!! :)
"3 Perfect Gems (of any type) + 1 Magic Item = 1 New Random Magic Item of the Same Type"
"1 Magic Ring + 1 Perfect Emerald + 1 Antidote Potion = 1 Jade Ring"
"1 Ort Rune + 1 Amn Rune + 1 Perfect Sapphire + Normal (Basic) Rare Weapon = Exceptional Rare Weapon"
" 3 Perfect Skulls + 1 Rare Item + Stone of Jordan = Add 1 Socket To a Rare Item "