Greetings,
If I read you correctly (and if I'm not, just hit me over the head with something), you want to play with all the new addons and stuff in the original missions/ campaigns?
Due to the nature of weapon selection (you have to tell OFP what weapons the player can have, you can't just tell it to include anything that's in your addons folder.
So this leaves you with two options:
1. (the short option): search for missions made by the community that contain the addons you like. Many of the quality addons have some missions associated with them, so it shouldn't be so hard to find a good quality mission that you like.
2. (the considerably longer option) Learn to OFP-Edit and mod the 1985 campaign/ original missions to include the new weapons and vehicles.
Actually, I seem to remember reading somewhere that someone was recreating the 1985 campaign (using all the original sounds and missions) to include some of the better addons out there. However, this could easily have been a figment of my imagination, so don't be too reliant on it.
Oh! of course! Option 3:
3. (the shorter than 2, but longer than 1): Learn to OFP-Edit (to some degree) and make your own missions in the inbuilt mission editor, using the addons you like.
I hope you find something helpful in the above...
. I apologise for rambling on. ;D
-Supreme Commander PsyWarrior
-Psychic Productions Studios