I think that ICE's HARP has a rather good system for handling "weapon proficiencies", although there still remains some complexity that could be streamlined.
- Weapons are classified into several classes (such as 1-handed edged, 1-handed concussion, and thrown),
- which are subdivided into weapon groups (e.g. for 1-handed there are 4 groups including long blades and axes)
- and further a default weapon is selected from the group. In summary, on might have skill for long sword, without the need to worry about groups and classes.
However, having the long sword weapon skill gives a bonus for using all 1-handed edged weapons and better bonus to all other long blades. The default weapon of a group can be changed by training for a week (for instance, from long sword to falchion).
Using the conversion mechanisms between Rolemaster and D&D 2nd edition :p (or just common sense;)), the rule could be quite easily adapted to d20.
(ICE offers the HARP lite (98 pages pdf of core rules) freely on their
web site.)