What's the best mod(s) that still lets you play vanilla Campaign?

[Cpt. Rogers]

Just as the title states, I'm interested in playing Campaign again but I want something different. Like new units and structures.

[Bob of Mage]

A number work for most missions, and you can easily skip missions if you are using a save that has beaten them already. The biggest issues are changes to missions causing certain units to not spawn properly (for example in the GDI mission to retake the White House the MCV doesn't spawn), and balance thrown off due to changes to the tech tree (normally GDI will get it's ass kicked at the Sydney Wall and you have to defeat the Scrin yourself, but while playing with one mod GDI turned the battle around so well I needed to destroy the wall myself to trigger the secondary objective before the Scrin were wiped out without me doing a thing to them).
EDIT: Also sometimes mods alter units in such a way that it bugs the version you get in a mission since it is trying to apply mission specific changes on top of mod changes.

[Azidoazide Azide]

I recommend Tiberium Essence because it's one of the most balanced mods out there and you can pretty much play campaign with it

[Solarfried]

Like Azidoazide i would recommend Tiberium Essence, there is so much funny and nostalgic stuff in it, only sad is some of the cool vanilla models were replaced with imo uglier custom oder Tiberian Sun models...

On the other side, you can try Red Alert History, if you are interested in a mix from all Red Alert titles...