I think that is probably the best(only) way we get him really. Right now he's a good option to rotate with some players, but he's not displacing any starters and that's probably not ideal for both him and Liverpool. However if he got to finish up the season here and then prove himself at Prem level, then Liverpool are getting a big benefit, we are, the player is.
Liverpool have stated that it's their intention to take him into the fold with the 1st team next season, I don't see how a championship loan helps them in that regard. There's not really anything to prove at Championship level. He needs to show he can do it at Premier League level, either with a Prem loan now or as you say with an 18 month loan to a team that has gotten promoted. Saints are in the mix for that, but we're the only club you could hang your hat on for it.