I am concerned because someone seems to have fed you a bunch of misinformation, and unfortunately we tend to believe most whatever we hear first. Technical diving is not some kind of high-risk, white-knuckle adventure. It can be safe and fun in most any reasonable environment.
Having a unified team actually increases your flexibility. When all your dive buddies have similar equipment and training then they're essentially interchangeable (within reasonable limits). Solo sport diving is always and everywhere a bad idea. You need someone to assist if you get entangled or have a serious equipment problem. Plus it's nice just to have some company and another set of eyes to spot interesting marine life. If you can't find a qualified buddy then just skip the dive; there is nothing underwater worth risking your life. There have been too many incidents of solo divers ending up dead for unexplained reasons, because there were no witnesses and no one to help.
The dive computers available today are simply not useful. The fundamental problem is that a computer can't accurately measure bubbles and dissolved gasses in your body. All they can do is run some simple, idealized models (i.e. "first assume a spherical cow") which are fairly close to what a typical person will experience during a limited range of dive profiles. For example, the models I have seen — including VPM, RGBM, and others — fail to properly account for the oxygen window during decompression and so will stretch ascent times out unnecessarily. A lot of divers lack the scientific background necessary to understand the difference between accuracy and precision. A dive computer will display highly precise numbers, but who knows whether they are accurate? Despite their limitations, the mathematical models are useful for understanding the general shape of the decompression curve across a spectrum of possible profiles. Once you understand that then you don't need a dive computer, or computed tables. No one I dive with would actually try to reference a table in the middle of a dive. If you want to waste money on an expensive dive computer then go ahead, just don't fool yourself into believing what it tells you.
Helmets are unnecessary for sport diving; don't dive in places where heavy things can fall on your head. A light on your helmet will blind your dive buddy when you look at him, plus having things stick out from your head is an entanglement hazard. Bring snorkel in your pocket if you want; it won't hurt but I've never found them useful. There's nothing wrong with bringing a bag of tools when you need them but please leave the wrecks intact so the rest of us can enjoy them, too.