There are two issues which over time became very frustrating in terms of Template creation,

1) Every time when we are copying the existing template (Copy the entire message in UI or extracting existing HTML code and uploading it in ZIP), when we try to save it we get an error saying - "Unable to complete request. Reason: An unexpected error occured. If the problem continues, please contact your system administrator"
We know that it's caused by markups or linkIDs from original message (mentioned in available Knowledgle article, but always there are some left, hence we are getting an error -t sometimes it caused by different problems within a code, like unclosed tags or spaces in images filenames)

This error is very generic and it's hard to find every issue by searching in lines of source codes. Also, article solutions don't apply to mobile coded images if they're separate from desktop, because these are not visible in UI.

Templates/Code validation is something that different platforms always had (at least the ones we used) and more specific information speeds up the process of fixing issues like that.

2) Loading zipped html package
Often it happens, that during the load of html/images in zip file, we receive an information that for example:
"10 files loaded, 2 files skipped", but we don't have any information which files were skipped and why they were skipped, which obviously can be problematic.