I don't think the number or nature of bills is to much of an issue as future patches and mods will no doubt add new and cool options.
What I find more concerning has already been mentioned though perhaps not exactly: essentially the system is at odds with itself.
On one hand we buy influence to get us more votes to win an important bill. These votes are expensive (the AI seems to want around 1bc for 1 IP which considering IP ranges in the millions is a lot) because the AI doesn't want to trade away influence in case an important bill comes up.
On the other hand you never know what bill will come up, so you never know if its important to you or not.
The result is, more or less, a stagnation to IP trading. No one gives away their own just in case they need that say but there's no way anyone can spend the mass of resources required to get a majority IP unless they're certain the bill is vital to they're civ, which they never can be.
For IP trading to be a worthwhile system it either has to be possible to do it on the spot (ie during the meeting) or you have to know the bills prior to the meetings. Then shrewd politicians (player or otherwise) can sell IP when they don't care about upcoming bills and buy it when they do. We'll know its working when we see instances of the AI coming to players requesting to buy IP, so long as the AI can afford to ignore IP trading it indicates that such trading has insignificant effect on the balance of power.
On an additional but unrelated note I would argue that, especially late game, the AI values its own IP unrealistically high. Even if I knew the UP was going to restrict evil trade routes to three, it would cost me, lets say 300,000 BC to get enough votes to win and maybe some technologies. I'm loosing 6 trade routes which, being generous, give me 1000BC altogether, that's 300 turns before its going to break even with the cost cost of the IP.
