If I were to stat the heroes of the lance at the start series, I would first normalise the levels. Using the 2e box set character cards, most of them are 4th level so I would make all of the heroes level 4.
I would stick with the classes they were given back in the day, most of the fighters would I would probably make champions, I might make Sturm a cavalier though. I would also upgrade some of the equipment, Flint would instead have chainmail instead of studded leather, for instance. Raistlin, having just joined the red robes I would limit his subclass choice to conjuration, transmutation, illusion, or evocation (I'm thinking back to the available schools in 2e and the specialisations available for wizard of high sorcery in 3e). I would be tempted to make him an invoker but I could see conjuration or transmutation easily fitting him.
Tika is probably the only one that I'm a little on the fence on how I would divide up her classes. Either a rogue/fighter or single classed in either and just use the urchin background for her proficiency in thieves tools.