I voted Remain (or Yes) as an 18yr-old, back in the 1974 referendum;
part of the reason was indeed because I wanted a United States of Europe
I was fed up with parochial national politics and wanted to use the combined talents of several countries, to find a better way of doing things.
The USE can only come about and be stable when like-minded countries naturally grow closer and closer;
if this doesn't happen, there is no point in trying to force closeness and it would be unethical anyway.
I would want a very high % agreement - at least 70% - in each country that joins the USE, plus agreed in advance a very clear constitution and the rights and responsibilities of member states.
So, I may be an "extreme" Remainer, but unlike the Brexiters I would not advocate my aims, until there is overwhelming consent for them
Naturally, there would be years of detailled planning first !
And of course, I wouldn't declare opponents to be Enemies of the People, or allow them to be intimidated.
Far from wishing to force Brits to Remain, I've always opposed a 2nd referendum
and I would probably oppose the Uk being allowed to rejoin after a Brexit crash
Referenda on in / out are fundamental, quite unlike votes on treaties, for which the terms can be changed if the voters choose.
The EU has never advocated re-runs of countries voting whether to join, e.g. Norway, Switzerland
And it would be inconsistent to want to re-run a vote on leaving
Although I wanted the UK to choose Remain, I think at this stage there is no going back - too many bridges have been burnt by this govt
The UK has always blocked progress in the social chapter and towards greater harmony
It has often - under Tory govts - been a wrecker
imo, the Uk should only be allowed to revoke A50, or rejoin via A49, if there is a very large majority for this
- a genuine enthusiasm for being in the EU, not just grudging acquiescence to avoid the UK economy crashing.
Back in 1974, we were disappointed that the vote was just under 2:1 
and we saw that didn't last. So, I would want a higher vote than that
There is a suitable place for the UK, or whatever is left of it after no-deal Brexit:
Norway ++ (SM+CU) could be negotiated to provide all the desired economic benefits, but the May's red lines would all have to go.
However, a future UK govt needs to balance benefits vs responsibilities / rules for each of the possible relationships with the EU:
Canada Dry, Canada Plus, Ukraine, Norway, Norway++
then pick one, explain why to the population and explain the required compromises.