A few years ago we converted the Aristocrat to a PC-level class for our campaign, too. It was nice to have, so that people who wanted a good class skill list and the ability to lead others didn't always take Bard levels (which gave spellcasting). We also totally reworked the Leadership Feat, but the version below uses the old Feat.
But, we didn't want to make yet another class with a list of bonus Feats. That just gets too easy. So, our changes (latest version):
Background: The term "Aristocrat" is more generally defined to be "rich, connected person". The PC picks one of the following backgrounds: Noble, Merchant, or Crime (the Mob). This affects many of the later abilities.
Optional rule: each has an alignment limitation. Noble can't be Chaotic, Crime can't be Lawful, Merchant has to have some neutrality (CN, LN, NG, TN, NE).
(Possibly add more: Scholar was a suggested one, but we thought it was too limited in scope and overlapped too much with Bardic Knowledge. Clergy was another suggestion; not everyone who runs a church is an actual priest.)
Contacts: (based on d20Modern ability "Favor" for the Charismatic Hero) It's like a CHA-based Bardic Knowledge check, except that instead of finding a piece of information, you're finding the person who can get you something (including information). This check can be done at most once per day (see below).
There's a bonus/penalty applied based on your background and how applicable your connections are.
First, there's a flat -5 penalty if you're attempting something outside your Background (a Merchant who wants to see the King, or a Noble who wants to hire an assassin). Note that there are some things that are outside every background.
Second, there's a question of how many strings you want to pull; for each connection you choose to draw on you get a +1 bonus to the check but can't use this ability again for an additional day. (That is, a +5 bonus disables for 6 days: one for the base ability, plus another five). You can't call in a number of favors higher than your Aristocrat class level at one time, and at the DM's discretion the cap may be much lower outside your home town (where you might not HAVE many contacts).
A successful check gets you access to what you wanted, but you still have to pay any other costs. Just because you found the best weapons shop in the city doesn't mean you get the +6 Brilliant Energy Vorpal Spiked Chain for free, it just means that without this connection you would never have known the shop existed/had what you needed.
For connections involving politics or information, there will usually be some sort of bribe involved. Also, this doesn't mean the target will be favorably inclined towards you; if you manage to finagle a meeting with the King, he might be willing to listen to you for a minute, but if you don't say anything that interests him it might hurt you in the long run.
(In general this is stronger than the Bardic Knowledge ability, but it can't be used as often and can be expensive. Be careful with it, though; if the players want to meet the king and they'd have the pull to arrange it on their own, you don't need to charge the Aristocrat for it, so only use this if it wouldn't be possible through normal channels. Not that you should tell them that, though; if they offer to bribe the chamberlain for a meeting he was going to give them anyway, he'd still take the gold.)
Natural Leader: All Aristocrats begin with something resembling the Leadership Feat, with the following changes:
> All followers and cohorts must be appropriate to the character's background.
> No positive situational modifiers to Leadership score apply to this, although the bonus for high CHA and any negative modifiers still count.
> Only Aristocrat class levels count for this Leadership score.
(Even though you get it at level 1, it won't mean much until you get to level 4 or 5 since you need a leadership score of 10 to get any followers.)
This stacks with the normal Leadership Feat. It's not uncommon for Aristocrats to take Leadership and have multiple cohorts.
Champion: Depending on your background, this could be called "Bodyguard" or "Hitman". Normally, your cohorts can't be higher than (your level - 1). An Aristocrat isn't as limited. First, the penalty for having a familiar/mount/companion is reduced to -1. More importantly, at every fifth class level (5, 10, 15, 20) the cohort level cap increases by 1, making it possible for the Cohort to be more powerful than its leader.
(That is, a 15th-level Aristocrat can have a Cohort 2 ECL above him. This'd probably be a "special" cohort, like a dragon, or something with a template. Optional rule is that the cohort's class levels still can't equal yours, which'd require this sort of exotic cohort; this way, you don't have an Epic-level spellcaster as a cohort. But, this ability is one of the big ones, to make up for the class' weaknesses in other areas.)
Inspire: Using the Diplomacy skill, the Aristocrat can get his allies/subjects/employees to do better. It works exactly like Bardic Music. The list of abilities depends on your background; the number listed after each is the number of ranks of Diplomacy needed to unlock that ability. The ones with asterisks are new; these are all (Ex) abilities, nonmagical.
Noble: Inspire Courage (1), Inspire Competence (5), Inspire Resolve* (10), Inspire Greatness (15), Inspire Heroics (20)
Merchant: Inspire Competence (1), Fascinate (5), Mass Inspire Competence* (10), Suggest (15), Inspire Mastery* (20)
Crime: Fascinate (1), Suggest (5), Inspire Competence (10), Mass Fascinate* (15), Mass Suggest (20)
The new ones:
Inspire Resolve: An improved version of Inspire Courage; all allies within 90' gain a +4 morale bonus against all mind-affecting effects, and get a +1 morale bonus to attack rolls, damage rolls, and AC.
Mass Inspire Competence: as long as the Aristocrat keeps giving his speech, all allies within 90' get a +2 competence bonus to all skill checks. Any skill incompatible with Inspire Competence also fails here.
Inspire Mastery: as Inspire Competence, with the following changes:
> The bonus increases to +5
> Take 10 may be used even if under duress
> Take 20 may be used even if failure would have consequences
> It works on any skill (as long as the Aristocrat is speaking the entire time needed to use the skill, so long Craft checks are still out.) This might still be counterproductive (for Move Silently, for example).
Mass Fascinate: as Fascinate, except it affects all targets within 120', except those the Aristocrat specifies.
(Each person only gets five options, and slower than the Bard does)