"Game Experiance Customization" - Cheating, in other words.
It has been confirmed that the Forge set of tools will be included with Sins of a Solar Empire, and no doubt it will be a sweet suite of tools. It's a bit overkillish for most forms of "Ah heck, lemme just fiddle with this" tinkering, though.
So, here's what I propose. A more rudimentary form of game experiance customization toolbar to be provided within Sins itself; disabled by default, you can activate the bar from within the options menu - after recieving a fair and clear warning that this constitutes cheating, the bar will become available, by way of a button that appears at the top-right of the screen, under the crystal resource number..
Pressing the button will make the bar appear below it, and here you can modify several variables.
The first option on the bar will be a drop-down menu - it helps to know who you're editing. This way you can edit yourself, the other factions, or both, as you please. This bar should display the faction's name, in the color of their flag - displaying the flag too would be nice, but unnesssary.
Under this of course, you'll have three basic options - credits, metal and crystal, displaying the current amount of that resource. All that's needed here is a simple text-entry field; when the player selects this, the field ceases to automatically update, so that the player may enter whatever number they wish. When they click on the icon, or press enter, the variable is updated. (Alternatively, you could simply have four buttons marked +, ++, -, and --, which will add or remove 100 or 1,000, respectively. I would advise against this, as my personal experiance has always been better with fine control through text than coarse control through set-number add/subtract, but YMMV. In any event, it should not be overly ardous to add both, if one were so inclined.)
Next, you should have the tech editor. The simplest way to do this would be to have the button for the tech editor bring up the normal technology screen, but with it's functions altered. Instead of starting research, a left-click simply adds a level of a given tech, instead of canceling research, a right-click removes a level of a given tech. This would be a bit of a pain in the arse to create, but hopefully not ardously so much. For more coarse control, and to simplify the majority of tech tree editing, you can simply add a "research all" and "research none" button, which maxes out everything, or zeros all the tech, respectively.
And finally, another drop-down menu listing the capital ships of a given empire, with a button to raise the ship's experiance level. May as well omit the lower experiance button, since that would give you a complicated mess, requiring you to either strip all the upgrades from the ship and re-apply them, or else save the upgrades in order of their selection, so that you could strip them off one at a time.
I think I hit everything that you could reasonably want to tweak while in-game, without going all-out and creating a full-scale in-game game-editor. Thoughts, suggestions?