Hiya,
Specific mods that need a new career 99% of the time say so in the readme (or whatever the mod forum post says for info on said mod/s)
That said, i have found that the only time i need to start a new career is when some new addition/change is made to the Menu, this is not cast in concrete so to speak
So while in bunker, eg as you say you want to add the sleet dynenv
That's an easy one
Save your mod profile somewhere handy (desktop for me, saves me hunting later on for stuff i mess around with)
You can edit this with notepad, easy way is this .............. then disable all mods
Open saved profile (mep) with notepad
Open jsgme, all mods will be on the left (you've saved mep and disabled mods)
Highlight on left side of jsgme and click Rename, you just copy that name of mod not rename, paste it where you want into notepad opened mep
Re-order add/remove do want you want
When you've created a new list as you say 'in order' just make sure you have your mouse cursor after the last text, and save mep (you can copy/paste mep beforehand to be safe, it will save as xxx.copy, this is still usuable)
This i find fast and easy, and to the point i never get the spelling messed up as i've copied the mods name exact as it's installed
Hope that helps
ps : as long as you don't add or remove any Menu altered mods you should be fine n dandy
pps : if you copy/paste your mods up i'll have an idea if you need to worry about a new career
Hope i make sense lol