Stretch goals for skill specialists?

[Varyon]

Originally Posted by RyanW

I dislike putting the mission behind a door only one PC has the key to. But bonuses are a different story. You can provide optional objectives with brief but challenging obstacles and their own little rewards to let characters' talents shine.

That's a good option. Have the mission-critical instances that require the skill be ones where the understudy's skill level is sufficient but then have further instances that are beneficial to the party but not mission-critical. Alternate (and safer!) entrances to areas they need to access, more loot/samples/whatever, additional gear/supplies, gaining an ally, etc.