I've heard that the PageMaker Plugin Pack for InDesign allows for importing editable .ai files. Would that help?

I can't find anything about that. do you have the url please?

http://www.adobe.com/products/indesign/pm_ind.html

After some digging, I think I found a better solution. InDesign ships with a script: AddGuides (Window>Automation>Scripts>Samples). This allows you to create guides around any selected object, and any of its sides/centers.

If you were to set your SG script to create objects which define the guides' placement, pasting those objects into InDesign is supported natively...

thank you!
you've got the point: now I'm trying to transform all my artwork into guides...
I don't know how to do that...

...can you help me please?

In Illustrator, it's simple; for a selected path, set the guide property to true.

for example:

var p=null;

p = activeDocument.getSelectedItems();
for (var i = 0; i < p.length; i++) {
p[i].guide=true;
}

this will turn all selected paths into guides.

thank you!

I'll try it immediately!

uhm, I can't make work your code...
it seems like nothing became a guide...

it works for me.. did you select the paths, click the script and press on the 'play' button?

Hmm... It seems to work just fine on every machine I've try.
Keep in mind, this only flips the boolean 'guide' value for a path, making it follow the Guide commands, such as Hide Guides, Lock ... etc. It will not make the path 'infinite' as a ruler guide appears.
If that's what you're after, you can transform the path to a huge length (227 inches on the x/y axis) so it appears to be a regular guide, or you can change the guide's starting and ending points with a text editor:
Each guide in a CS3 .ai file has three lines describing the starting point (X,Y,m), ending point (X,Y,L), and termination/path-type ((N) *). In a 10"x10" document, the following will describe a horizontal line at 5":

• 7831 360 m

8552 360 L
(N) *

The specific X values here are the most important - a guide MUST have a starting point at -7831, and an ending point at 8552 in order to be treated as an 'infinite' line. The same applies for vertical guides, but in the Y coordinate. As well, (N)* terminates a guide, while N ends a regular path.
If you create all of your new guides with the same X/Y positions you can easily search and replace the right values to fool Illustrator into thinking it's full of regular ruler-guides.