You can't stop good old "Rxb" from changing rules. Everywhere he goes, he sees rules that are "clearly broken"--and he just goes and makes them "elegant."
There is a simple trichotomy in his gaming universe: something is clearly broken, elegant, or (rarely) "clever." It's a well-ordered universe, and you always know who your friends are.

Rxb informs me that, in theory, a game (or a mechanic) could also be "arbitrary" -- somewhere between "clearly broken" and "elegant". In theory. Such situation still demand fervent remedy, and should be treated as no better than "clearly broken". Upon attaining elegance, the less ambitious may stop and rest upon their laurels, but the driven will still strive for the nirvana of "clever".

I received this question by geekmail, and felt that others might also want to read my clarification:



IS IT NECESSARY?
Nope. The game works just fine without the variant rules. However, the basic game is more cut-throat, and it's easier to dig yourself into a hole if you don't know what you're doing. The variant rules make the game more permissive, and thus more appealing to beginners. Hard core fans may still like the standard rules, or they may prefer the less intense variant.

NORMAL RULES
Under the normal I.V rule, any 3 cards of 1 color can be played (discarded to the pool) as a Jack. This means that you can you can lead a Patron role by discarding 3 Laborer cards, or follow a Craftsman role by discarding 3 Architect cards. If you have the circus, you may instead discard 2 cards of the same color as a Jack. That is, you might discard 2 Laborer cards to lead a Legionary, or discard 2 Architect cards to follow Laborer.

MIT SECRET HOUSE RULES
Under the variant rules, everyone always has the old Circus power. That is, you can always discard 2 cards of the same color to lead or follow any role. E.g. 2 Laborers could be used to follow an Architect, or 2 Legionaries could be used to lead a Laborer.

Since the old Circus building card would be redundant, it instead works like this: When you have this building, you can play any card of any color to lead or follow an Architect. That is, you might play a Laborer, but declare that you are leading Architect. Someone else might lead Architect, and you could follow by playing a Legionary.

MOTIVATION
Giving everyone the Circus power by default helps beginners because it means you don't get locked out of the game. If you have 5 cards in hand (e.g you just took a Thinker action), then there is at most 1 role that you cannot follow (do the math). If you haven't figured out how to make good use of Laborer, you can get rid of your Laborers by using them as Craftsman. If you overspecialize your strategy around 1 role, but don't draw any cards of that role, you can still execute your strategy (by petitioning for it). Also, because people petition much more often, there will tend to be more cards of more types in the pool. This means that it will be easier to get the type of client you want when you play a Patron, which makes the game much less vicious.

Changing the Circus power makes Architect competitive with Craftsman in power. Normally, Craftsman is strong throughout the game, and Architect grows in power as the game goes on. The new rule for Circus provides an early-game strategy using Architect, and helps to balance the two roles.

Even if you are playing with an experienced group, and decide to play the more vicious 3-for-1 petition rule, I recommend still using the variant Circus power. It makes Architect a much more interesting role.

Addendum:
Further testing of the house rule has revealed an additional change that is needed under this variant. The Forum is a building that makes you win when you have 1 of each of the 6 clients. Change it so that it also requires that you have 1 of each of the 6 materials in your stockpile. Otherwise, it is too easy to satisfy it's goal simply by petitioning for patrons a lot.

Of course, if you are playing by the regular rules, DO NOT change the Forum. This is change only works with the 2-card petition variant, although it is rather important under that variant.