You could call it 'guidelines' but it's no biggie to throw a rig hook onto one of the cross beams of a platform. You just have to give the supply boats the right away, and I can tell you from working in this industry, you have a very small chance of running into a supply boat the same time you are fishing near a deep water platform. Also, tuna do not always hang close to the platforms.
Venice is a great place to fish out of, but don't talk people into towing their 21' center console boats down there to go tuna fishing. Not enough boat for the distance you have to travel to get into tuna water, even though you are protected when running the Mississippi. Ever seen the wake that a 500' cargo ship puts out?.
But the OP has the right idea, hire a guide boat and you will all have much more fun. The action is hot right now and it's NOT coming from the rigs and platforms. The rip-line has been only 10-15 miles out over the past few weeks. Made a trip 2 weeks ago and loaded up on Mahi Mahi, 1 tuna, and hooked into 2 blue marlin. Those bull dolphin (Mahi Mahi) are a blast to catch and eat better than yellowfin, IMO.
Right now we are trolling the rip, pulling Stretch 30s, Islanders or Rapalas to pick up anything from blue marlin, Mahi Mahi, wahoo, and yellowfin tuna. Sometimes the mahi will be still long enough and you can sight cast to them. Talk about a blast!