I'm hoping for more of a skill system, similar to FFXI. The more you use the skill, the more it goes up. In FFXIV's skill system, hp and mp would be considered skills and every time you take damage or use mp, your skill might increase. For every skill point, lets say you get 5 hp or mp. Now, since your level won't be capping your skill level, I think armor will not only act as the cap for your hp/mp, but it will also allows you to utilize your HP/MP skills on your character.
For instance, lets say you just started out. You have no armor on and 40 hp due to your VIT stat. Your HP stat is at 0 and can't rise without a piece of armor to raise the cap. You obtain a brass harness with +5 HP skill on it, which allows you to level your HP skill to level 5. You equip it and go to grind on some monsters outside the city, you take damage which levels your HP skill. Every time your HP skill levels, you gain 5 more HP. You cap your HP skill to the level your armor allows(level 5) which gives a total of 25 HP, giving you 65 HP total.
Now, you do a couple missions and get a Scale Mail with +10 HP skill on it. You equip it and your HP skill is now at 5/10. You level it to 10/10. You now have 90 HP with the Scale Mail equipped. But if you switch back to your brass harness, you will go back to 65 HP since with that armor only allows the use of 5 of your HP skill.
Basically, its just like FFXI's skill system but all levels of growth are based off of skills. Armor will be the judge of how high we can level them and to what extent we can currently use.