I'm fairly new at using blogging software so this may be a stupid suggestion.
Because this was my first blog I keep realising that I need to add and merge categories. A problem arises when I want to order them by ID number. I use the ID to create a unique order that is not covered by the options in WP. Every time I add or merge cats. I have to renumber the ID's. I do this via phpMyAdmin which is great but would prefer to do it from within WP. Admitedly I don't do this very often but it still happens.
So, here's my suggestion. All new installations of WP have ID's starting at 10 and continue every tenth number; 10, 20, 30 etc. Now if you need to insert a new category you can number it 14 (or whatever) and this means you can control the order. Of course you would have to add the ability to change the ID from within WP and I don't know how easy or hard that would be.
Whilst it's easy to say "Well think carefully about your categories before you create them", you have to remember that often a blog grows along with the author or authors.
Only for the oldies here: I remember in school when I was knee high to a grasshopper (very young, well 15 anyway) We started to learn B.A.S.I.C. and were always taught to number the lines of code 10, 20, 30 etc. Of course most code I see doesn't have numbers anymore. Old habits die hard!