While I know what you mean, I do still want there to be a method of adding friends though, so I wouldn't ever want them to remove that ability completely. (but yes, I totally agree with you that the current system is quite a cumbersome process, due to both users having to add eachother's friend codes from both ends, and not necessarily knowing what their ridiculously long and easy to mistype code would be in the first pace, -even for people you know in person!) it usually requires alot of hassle making prior arrangements exchanging them beforehand, so not quite so practical in real time). Ideally it would have been better if only the inviter has to put in the code, and the other side just accepts you the other end, just like you do on skype, for example. (even better if you could send friend requests via email address rather than a friend code. That way you could invite any or all of the friends you know who also have Nintendo consoles, just be adding them via email address). It's so easy to tap in a friend code in wrong. But I do get why they do this (as if you add online friends that you don't know so well in person but you just want to play with them because they like the same games as you, you don't necessarily always want everyone knowing your email address). But having the option to do this where it gave you the choice of using either method would definitely be a good way to solve that problem. (unless you know of a better way).
Adding via username, or by tapping the mii (in game) of random online players that play the same games as you would also be a good additional method of solving the problem, and it would also be alot more secure than via the email address method in instances where you don't know people so well.
If it were up to you to design the friend request system, what do you reckon would be your ideal method?