I think most people would want us to stay in the EU as a trading block, which was what was originally voted on in the referendum back in the 70s. However, most people in polls say that they want radical reform, and those results are reflected in many countries across Europe.
The idea of us all working together is a good one, but there needs to be more flexibility, so that countries can opt out of particular rules. Currently if a country doesn't agree with a decision they tend to ignore the rules, except us of course.
The real problem with the EU is the institution itself, massively bureaucratic, fraudulent and wasteful, nothing more than a gravy train for failed politicians, which is why no matter what the public want, politicians carry on supporting it. How obscene is it that their own auditors refuse to sign off the accounts, as they have done for many years now, simply because they don't know where all the money has gone. And yet our politicians continue to pay money in on a scale that makes the expenses scandal look like peanuts.
If we were to leave, or insist on changing things radically, there's nothing anyone could do really. If we stop paying in, then they can't really do much about it, if they fine us for not following a particular protocol, we could refuse to pay the fine...something France has done many times. Ultimately then yes, they could add tariffs to our exports, but trade works both ways and most EU countries are heavily dependent on the UK importing stuff from them too, so a trade war is very unlikely as both sides need each others business. A recent report by LSE (I think) suggested that in a couple of decades we would be the biggest economy in Europe, bigger than France or Germany, not just because our trade is more open / less bureaucratic than on the continent, but also, many of the booming countries....China, African continent, etc, have closer links to our culture / language so we should not be too afraid of any falling out with the EU.
The Loose cannon is always France as they tend to rule with their hearts rather than their heads. I think it was during the Iraq war they tried a trade embargo on the US as they disagreed with it. This did France a lot more harm than the US as France then found it hard to import any cheap goods from the US that they wanted, but at the same time, French goods, (Champagne and cheese basically), wouldn't sell in the US. Most countries across Europe take a much more pragmatic approach.
I think what happens with the EU in general in the future, will depend mainly on what happens to the Euro currency, and that's not looking positive, but many politicians have their heads in the sand about the issue, and it will be the markets that ultimately deal the final blows.