Down near the bottom, probably relegated with the current squad. Don't think they would ever make it beyond relegation strugglers and think the fans would get pretty sick, pretty soon, when they're getting hammered every other week.
Sure, they've got a fan base, but good luck trying to get enough stars to want to live in Scotland and play there every other week.
They would need an absolutely massive cash injection, probably near £500m to be able to have a chance to get top half, but who is going to do that? Even Newcastle tried that and found it tough, they're rich and in a better location than Celtic and even they struggled to get into Europe. Man Utd finished below them and West ham or Brighton would walk the Scottish league.
People always get the wrong idea because they compete with prem teams once in a blue moon in Europe, but for Celtic players and fans that's probably the main aim of the season, to win that game, where as English clubs would be looking at that as just a normal game, and the big teams would possibly be resting players.