Eminent Domain: Politics alternatives?

One thing I'm still a little worried about for Eminent Domain is game length and game end conditions. The last thing I want to happen is for a game to end too quickly and not be very rewarding - and that's very possible in certain cases - mostly it involves newbies or poor play, but frankly, everyone will be a newbie the first time they play, and until you gain some experience, many people will play poorly because they don't know any better.

In particular, I worry that newbies in a 3 player game will drill down to the bottom of the colonize stack way too quickly, ending the game early with low scores all around and a disappointing feeling of not having had time to get anything done. In a 4 player game the game end condition is *2* piles, so the concern is lessened there, but I also worry that if everyone sort of copies each other and takes the same couple of roles over and over, that game could end prematurely as well. Simply adding cards to the piles doesn't really fix the problem - because it adds significantly to the production cost, but more importantly because then when players don't drill the same stack, the game drags on far too long.

I've currently got the following distribution of cards in the stacks:
Colonize: 20
Research: 20
Hearvest/Trade: 16
Survey: 16
Warfare: 16

And it has been working alright. In order to try and ensure that my concerns don't materialize, I would like to find an alternate use for Politics - one that maybe does the same thing the current Politics card does, but doesn't remove cards from the stacks. Here's the current card text for Politics:

Action: Remove this card from the game, then take any 1 Role card into hand.

The idea here is that the Politics card helps you customize your starting deck, by effectively turning into one of the other Role cards of your choice. I like the dynamic there, but would like to find a way to do that without actually removing cards from the stacks, which shortens the game length.

One idea I had was to change the wording to this:
Action: Boost the Role played this turn by 1. When this card would go to the discard pile, remove it from the game instead.

This is exactly the same effect, only you aren't left with a card of that type in your deck. I liked the sound of it at first, but it's a little wonky when you look at the Colonize Role - technically, if the Colonize role is boosted, that would have to be noted somehow. I suppose the politics card could be placed behind a planet as a colony, then when the planet is flipped, the Politics card could be removed from the game at that time - but that's very clunky and counter-intuitive.

Any other ideas? Please post them in the comments! I wouldn't even mind other effects that the Politics card could do, different from the current one.

I have some thoughts floating around for an expansion which would come with a stack of Politics cards, and would add Agendas to the game - the Politics Role would be how the Agendas come into play. Then the Politics card would be in your deck, and later when you draw it you could use it for it's "Action:" effect. I suppose that doesn't matter much for the current problem though.