1. The vote must be a minimum threshold and an explanation of what happens if it is 48%:52% say. maybe if it was a minimum of 70% and that wasn't achieved then Britain goes ahead with Brexit BUT with a cross party steering group to ensure buy in from all parties. Anyone who thinks that is wrong? Well what happens if there is a war? Do some parties say we aren't interested we vote against war as the enemy land on our beaches?. This latter point sums up what has gone wrong so far but then Cameron started the rot with his lack of clarity on what people were voting for plusses and minuses and a minimum threshold.
There was no threshold on the original referendum, and I doubt there would be one on any new referendum. If there were, then it would be more likely the other way - the status quo rules unless 60/66/70/whatever percent want it changed. The status quo is that we are currently in.
2. Stay as we are needs explaining as I doubt we would keep the opt outs plus the UK would be a cowed version of its previous self despite outwardly being welcomed back warmly.
Stay as we are means exactly that. If we are legally allowed to withdraw Art50, then everything reverts to as it would have been had we never invoked in the first place. We never left, so there would be no welcome back.
3. A cast iron legal guarantee to offer the public a vote in x years time (say 15) so that in the (in my view likely event) of the EU failing to reform that we could get out. A lot of older people , myself included, voted out because they could not see any reform, only greater federalisation with ultimately having to take the euro etc. The timing of the vote was questionable but it was possibly the ONLY opportunity ever to vote on "EU" having joined a "common market" That legal guarantee might make Junckers successor think hard about change having just averted disaster in terms of losing the British cash cow and the ensuing trade friction and years of distrust on both sides of the channel.
In the UK, Parliament is soverign. No parliament can bind a future one to do (or not do) anything. If one parliament passes a law, then the next one could revoke it. However the EU rules would remain so Art 50 would still be there and if parliament decided to do so it could invoke it again at any time in the future.
One option might be to pass a law which stated no future EU treaty changes could be agreed by the government without the agreement of parliament and a public referendum. The government can be bound by parliament. This would effectively freeze the EU as it currently is. No additional QMV, no EU army etc. Wouldn't be very popular in Brussels though.