If they moved to the energy slot, they would certainly have to be nerfed in some capacity to bring them in line with other specials. Part of the reason I think this is such a hot debate is because of bungie's choices regarding slot changes from D1 to D2. Now that primaries are available in the energy slot, moving ANY weapon around is a sticky subject. If LFR's had been introduced into the special slot from the beginning, I think they would be well balanced with snipers shotguns and fusions and offer a unique playstyle, because they would have been purposefully balanced to make them useful in particular situations but not ALL situations. I keep seeing the argument that they are inherently better than snipes due to high damage, fast charge, low zoom, etc. If they had been balanced as special weapons, I imagine the charge time would have been slower and the damage would be lower. Still capable of one hit kills to the head, but at the cost of requiring that charge up to do it. Head to head a sniper would kill you faster with its headshots simply because it can land it faster in trigger pull and snipers would win out in body shot TTK too, again because of trigger pull time. However, the fusion would be the better gun with the right playstyle due to its wider FOV while ADS, which means you could be closer to your opponent and force them to get a body shot while you land your critical hit. I'd say the same basic principle applies to scouts versus auto rifles. Scouts are meant to be long range and can shred auto users due to less falloff and the ability to land your crits. In theory a scout at close range could still kill faster than an auto if it you landed your crits, but it's more difficult to do so at close range whereas the auto can certainly land them. A faster theoretical ttk falls apart in actual gameplay.

Agreed, linear fusions are ten times easier to get headshots with and have a really pathetically small charge time