What if one were to alter the Dwarf and the Hobbit/Halfling and make them so they function as two differing classes or may multi-class, like the Elf does?
I suppose I should add here that I grew up on B/X, and mostly 1st edition, so this is probably where my heretical viewpoint comes from

But I was toying with the idea: Have a dwarf able to choose to be a single classed fighting man as written, or perhaps a single classed cleric up to 5th, or allow them to choose which to level between each adventure. I thought about allowing those who chose single classes to progress to one level higher (7th fighting man, 6th cleric).
Much the same for the Hobbit/Halfling. Choose single class fighting man (4th level), single class cleric (5th? 6th?), or again like the Elves, swapping between the two after each adventure (again, allowing single classers to go one level higher). Campaigns that use the thief class would (or could) substitute the thief for the cleric in multi-classing like Elves for this race.
Any of you guys try this before? If so, how did it play? Did you have a positive experience with it, or did it not turn out how you intended during play? Just thought it would be a fun thing to discuss.