Many will be using the tag man for 3rd party marketing tags. This is not very flexible today and can easily become crowded when using many tags and conditions.
Suggestion:
Make it a 2 step process:
1) Add tag name/category eg Doubleclick that will appear on the same level as Adobe Analytics
In the overview add a tag.
Make it possible to name a tag and then add the custom script
It should be possible to add several indenpendent tags under one cataegory "Doubleclick" eg
"Doubleclick Retarteging" and a custom script
"Doubleclick Order page" and a custom script
2) Go to Rules
In a dropdown it shall be possible to select the newly ceated tag in a dropdown after the GA/Adobe.
eg. select Doubleclick > "Doubleclick Order page" and then make a rule for that