Yep, giving players a reason to develop the skills beyond 20 is exactly part of the reasoning behind it.
How it works is, if you are a Pure Arms user, you pick a specialization tied to a weapon (only two are allowed - the idea being you could specialize in one melee and one ranged weapon/style) and as you gain ranks in that weapon you gain the benefit of the specialization.
You get abilities at ranks, 2, 5, 8, 12, 16, 20, 25, 30, 40, and 50. Each ability takes a certain amount of Exhaustion Points to trigger, although a few are intrinsic/permanent (for example at rank 20 in the weapon skill you start gaining +1 per rank developed after rank 20 in order to combat diminishing returns).
If you want to be a generous GM you could say that the 1H/1H style applies to all 1H weapons, or you could say one type (Slash, Krush, Pierce), or you could say a specific weapon (a Broadsword for example). In this way various GM's could limit the power of the skill to some degree per their own preference.
I could figure out how to upload the a word doc if there's interest in it.
Let's see if this works... this is the 1H Weapon/Free Hand style...
Keep in mind this is RMSS based.
1H Weapon/Free Hand Specialization
Rank End Description
2 1 Quickdraw Character may bring his or her weapon to bear without using an action.
5 3 Parry Parry is increased by 50%
8 1 Shift Item Character may shift an item on his/her person without penalty to OB.
12 None Iron Grip Fumble Range is either halved or reduced by 2, whichever is higher.
16 5 Non-Weapon Attack Character can make an unarmed attack (using the brawling skill) on his/her foe.
20 None Expertise Gains +1 to OB per 1H Weapon rank developed from 20th level and up.
25 4 Dodge Ranged +20 DB vs. one ranged attack
30 6 Dodge Melee +20 DB vs. one melee attack
40 1 Adrenal Defense Character may use Adrenal Defense using a single 1H sized weapon.
50 5 Movement Master Character may perform a full moving maneuver (not additional attack) or move 50% of its normal base movement rate and make a full attack at no penalty to OB.