Role selection + bidding

Hi all. I'm working on a game design that utilizes role selection
similar to TI3 and Puerto Rico. Since it will make the game a bit
different from TI3 and PR and also fit the theme/back-story I have in
mind, I want the players to have to bid on the roles they want as
opposed to the first pick circling around the table. What do you think
would be a good bidding system for this? Right now I'm leaning towards
a system similar to Amun-Re, but I could use some feedback/suggestions.
I'm not huge into bidding games so the only systems I know besides
Amun-Re are the ones in Modern Art.

In case it helps, the roles are currently:

Control Jump Gate - This gives the player control of the jump gate needed
to export materials and goods from the system. Since this is the primary
means of acquiring VPs, the other players may be able to export as well,
but they will need to pay some sort of fee to the player controlling the gate.

Import Equipment - This allows the player to import extra mining equipment, factories, and freighters into the system. Mining equipment gets you raw materials, factories are used to turn raw materials into more valuable manufactured goods, and freighters ship the materials and goods out of the system for points.

Research + Development - This allows the player to acquire schematics for manufactured
goods that make for more valuable exports than raw materials. Ex: exporting X = 1 VP, exporting Y = 2 VP, manufacturing Z requires 1 X + 1 Y + factory, exporting Z = 5 VP. There may or may not be technologies other than manufactured goods as well.

Recruit Mercenary - This allows the player to hire mercenaries to act as pirates against opponents' freighters or to defend his/her own ships from pirate attack. The mercenaries should be an unappealing pick at the beginning of the game, but will become less expensive as more of them become available kind of like the cards in Through the Ages. Ex: new merc costs X, last turn's merc costs X-1, merc prior to that costs X-2`, etc.

Capitalize - This gives the player extra funding for his mining operations. It is basically the Prospector from PR.

Import Equipment and/or Capitalize may be doubled up depending on the number of players in the game.