Fancy exhaust ideas

Hi All! Hope to pick up some brain.

I am thinking to upgrade my exhaust (80LC 1HZ+DTS turbo) and do not like to think about anything less then 3” mandrel. But being maximalist I think to go one step future.

Exhaust in 80 diesels is really ugly. Not only it is more like corkscrew rather then pipe, but also it going above frame in two places – immediately under driver seat and where rear axle is. First position not a big disaster, but 3” pipe only barely can be squeezed in second place. I have asked exhaust person “How about make it straight, fit small low-restriction muffler and relocate it on another side of frame (i.e. close to side of the rig; understand all issues if decide to put rails or whatever later) and dump gases to side before rear wheel?”. Thus I can have incredibly straight virtually no restriction exhaust (ISVNRE, he-he-he). No problem. But there are legality issues. Apparently pipe has to be well behind rearmost opening. Ok. How then to weld to exhaust tip of ISVNRE existing piping and put valve. So when valve is closed all gases going by new ISVNRE and final piece of existing pipe, but when it open then gases dumped immediately before rear wheel gaining from my ISVNRE as much as possible. So I can keep it closed for everyone who concern and open in free areas. No problem, cost a bit more, but can be done.

Now the question. Is anyone can tell me if I notice any difference between imaginable ISVNRE and ordinary 3” mandrel going standard route? My brain tells me “No, you will not see any difference”. At the same time my devil says me “But you will be able to proof it. And while valve open you cannot get it any better”. Brain reasoning “But WTF? You going to use final 2” standard pipe on road and thus kill all gains of ISVNRE and only will use it off-road (i.e. less then 5% of time and even less of distance!). Or you going to breach the law and thus risk heavy fines.”

Any thoughts?
Thanks.
Serg.