I have been unable to think of any real drawbacks to changing the multiclass prerequisites, but I also haven't had enough time with the 5e system to make a good judgment on that.
My question is, what are the potential problems, if any, that could arise from changing the prerequisites for multiclassing for any class?
Some background:I have a player in my game who is playing a finesse-based paladin (he's playing a pirate who took the Oath of Vengence -- a "piradin," if you will) and he rolled pretty poorly (yes, we went with rolling 4d6, drop the lowest, if you remember my previous question) on his ability scores. He stuck with his rolls and has a 6 for his STR score. This is our first time playing 5e together as a group, and none of us realized that in order to multiclass you need to meet the prereqs for both classes, not just the one you are multiclassing into.
He wants to multiclass into rogue, which makes great sense for his character, but is restricted from doing so because of his very low STR score and the requirements for multiclassing as a paladin. I offered to let him swap some of his abilities, but none of his other scores are much better and would still be pretty restrictive in terms of multiclassing. Swapping his DEX and STR would break his concept, since he's going for a swashbuckling pirate type character, not a STR-based heavy hitter.
Thematically it works out great for his character and I'm leaning towards letting him multiclass into rogue because his attacking ability is DEX (he's a finesse fighter), and he would meet the requirements if it required DEX instead of STR.