Bad idea... Would essentially make everyone running with resist able to wear 5-mod armor pieces all over, with only the Exceptional bonuses in resists.
On the other hand, if one allowed the following, it might be more balanced.
Have it to where Resist gives one of the following to its user:
1. Its current resist, if the person's normal resist is lower
2 - one of the following, if the armor is better than the skill-provided resist:
2.a. Either raise the person's resist caps by 10% of the Resist value from the skill (1-4%, and make it 5% at 120 skill), or
2.b. Have it add that 10% value as in 2.a. to their resists.
2.c. Both a. & b.
2.a. would probably be a little more useful (especially when one is dealing with magic that affects resist)
2.b. would make suits a little less resist dependent, or help fill holes in existing suits.
2.c. would probably give an unfair advantage to those already with 70/70/70/70/70(75) suits.