I'd like to go on record and make clear that while i despise the stupidity of the majority of brexiters (we'll get all the deals, WTO rules best thing ever, for the queen!), this attitude is as stupid.
No. What Corbyn asked for to back Mays deal is unrealistic. He might as well have asked for a guarantee for a cold fusion reactor by the end of the year.
First, and that seems to be part of your problem, the EU will not agree on anything he asked for (especially not the part where he asks for a say in EU trade questions). And make no mistakes, these demands are not decided on by May, but by the EU.
Your problem is that you live in Lala-Land. It's right next to Brexit Empire on the map. You assume that the EU will shit on its own rules to accommodate the UK. Which is an extremely moronic thing to do, that's not how politics work. People like you argue that "yeah but it's also in the EUs interest to get a deal with the UK" - and that's right. But what you conveniently like to leave out is that the UK isn't special. Whatever the EU gives in concessions to the UK, they'd have to do with other countries too - and that's where the rats tail starts.
They have lines. They made them vastly clear, if by now you haven't understand that they will not, under no circumstance, budge on these lines, you need to wake up or shut up. There's either free movement, or there isn't. There's no "a little free movement". That doesn't exist, and btw, it can't exist either because that literally would spell the end of the EU.
That's what i mean by Realpolitik. Not wishful thinking that's based on shit for which there's zero indication it would work. Not once, not in the slightest, has the EU budged on the principles the EU is built on. To now argue that because Corbyn suggested it, it could work, if... is as dangerous as the "NO DEAL OLOL OGOG" of brexiters. It's wasting time.
That's something the UK doesn't have anymore. If anything, and here's the actual real problem, Corbyn should be be publicly condemned for these demands, because they, for all intents and purposes, make sure that you will have a no-deal brexit.
Sure, the EU might throw you a bone and call it "an advisory role on future trade talks", which basically would mean jack - but even then, this entire show is a clusterfuck. In case nobody has noticed, he's the leader of the opposition. There's not much "opposing" here, which leaves 48% of the country (back at vote day) without political representation. Not because it's "Labours stance" but his stance.
He's not doing his job, he's an opportunistic crooked politician just like any other (albeit for different reasons i suppose), i said it before and i again expect plenty of flak for it. He's not doing anything to indeed prevent the catastrophe that's looming not far away - he indeed facilitates it.
edit: i btw apologise if i sound like an ass, too.