rezulin, I found it quite easy to do the exact mod you requested I will outline the steps needed
1 get/create a set of reference files for entrenchment
2 create a new folder in the mods-entrenchment v1.02 folder and name it something like "sb increase"
3 copy the program files\sins\entrenchment\entity.manifest into the new folder
4 from the reference set copy the starbase*.entity files to the new folder
5 open in notepad or similar PLAIN TEXT editor each of the starbase*.entity files
6 in each of the files look for a line containing 'maxUpgradeLevelCount' with a number at the end
7 change the number to what ever you want
8 save the file
9 start entrenchment click on options then click on mods you should see in the lefthand panel your new folder as a mod click on it then click on enable mod then click on apply.
10 play a new game of entrenchment to test the mod
if you completed this quick course, CONGRATULATIONS you are now a beginning modder
harpo