Minigun cannot be introduced as you think, because the hard cap for rate of fire is 300 rounds per minute in this game. In fact Heavy blaster already hit that cap in most builds (standard with rank 11 implant is 297 rpm)
The sequence cannon is just a coil mortar with burst damage. While it can be interesting, it is more of the same at the end, and we already have alpha damage guns (positrons)
usually you can implement weapons like the minigun as hitscan weapons in such a scenario (see vulcan cannon in descent), also you can create an animation which seems to shoot faster / animate more shots on the client, and only balance it via damage calculation - like the laser, the minigun would fire a continuous burst, but only hit in periods.
technically you would have to balance it to the rof of other weapons anyway. All “limits” in the game engine usually correspond not only to limits in the simulation (more visual problems / continuity problems above certain values, like 700m/s, or 300 rpm in our case, rly depends on engine and scale), but also to limits in the balance.
however for me assault rails are pretty much the machinegun, i would rather see a gatling on a dread one day; after all to use a gun like that, you should also feel its power, the recoil, etc. so it has to be done right, if you want to use it in a space setting with death rays and force fields. I assume every weapon we use atm. is way more deadly, as our ships have also shields and highly complex armor, and we are accumulating the rarest and heaviest elements in our freetime.
so basicly i agree; however I think when we suggest stuff, we should not immediately think about limits too much. while i am not sure, what a minigun would add to the game, it would be certainly possible to implement it, to feel like a minigun, theoretically, all i’m sayin 
but it would certainly be weird as em weapon.