Over a short time, yeah, but over a whole quest you may well end up fighting without DM at times. Then, I dunno. But no dwarf or WF is going to start with a 16 Cha. Also, rather than looking at endgame, look at the beginning...the -1 to attack (from a 14 rather than 16 Str) will make a somewhat noticeable difference, while that 16 Cha early on will have little impact (almost 0 at level 1, and not much for a while, since the enhancement line doesn't come in until later, and even then, the same could have been achieved with a 14).
Personally, a decent adjustment to this could be allowing ability score enhancements to count toward base ability scores when qualifying for enhancement prereqs. After all, the only way you are going to remove the ability+ enhancement will be by respec'ing and thereby also losing the DM at the same time, so no conflict should occur. And that way, paladins won't have to rely exclusively on +2, +3, and +4 tomes to reach the upper echelons of the enhancement. And it isn't as though this will make things easy...paladins are already squeezed for AP, so even taking that +2 or +3 Cha for 4 or 6 AP will be a significant sacrifice. Easier for a human, but not much.