To roll or not to roll
4E is a very good combat rule set. For non combat it lacks much. Yes those of us that played before skill where invented used ability checks for everything. However, the ability check does not allow the player to really excel at given areas.
The thing with most players I've had is that they like to roll dice. If they are not rolling dice then they get bored. Many role-play situations are run without rolling dice and that causes the players to get bored.
Now when a player rolls his/her dice they want to know what it takes to succeed. If a player rolls dice in a social setting or non combat setting, the DC/TN is a bit grey. They have wonderful stats on their character, but the GM likes to reward the extremely well played role.
The bad part of this is a person with a 20 charisma is much more charming than the average gamer. On the flip side the PC with a 8 Intelligenc may not be able to deduce the same as your player. So the player rolls their dice. A number comes up, the poor GM has to determine if the modified 33 that the player just rolled is good enough to talk his way into the king's audience chamber. The character is covered in gore, limping badly and weilding a blood soaked greatsword.
"But I rolled 33"
No game system can cover all the areas of non-combat RP, but 4E does not even put forth a reasonable attempt at it.
Skill challenge = complex skill check (Alternity)
3rd Ed was much better for RP. Classes for RP. Prestige classes for RP. SKills for RP. Feats for RP.
What 4E skills would you use for a bard performing? Diplomacy, bluff, intimidate.
The "social skills" are just there to enhance combat.
Forge a sword? arcana, thievery, nature, dungeoneering.
4E is trying to appeal to the masses who do mostly combat. But it has massive blind spots in non combat areas. The best hope is to wing it or establish a set of feats, class features, and skills that are for RP.
Give selection of a trained RP skill as a background feature. (4E thought fewer skills = better) for some it might be.
This could also be followed with paragon classes modeled after some 3.0 presitge classes.
(3.5 was a waist of my time. 3.0 worked just fine.)
For influence rules to use, check out the now dead A Game of Thrones D20 system. PDFs can be had at an online PDF vendor.