Experience at the QB level. Once the QB doesn't need 4 or 5 seconds to throw and can throw into tight windows more consistently, then I think the offense will actually be better.
As for adding players? IDK, after Watkins wasn't fully utilized (IMO)... I guess more players that fit McVay's system and to get rid of the ones who don't. Or maybe McVay just needs some seasoning at the HC position.
Not sure about the defense. The draft might help. I feel certain they will add a payer or two who fits Wade's scheme... and lose a few who kinda don't.
Another thing they need is to stay healthy. I have never seen a team stay as healthy as the Rams did last season.... even Saffold for the most part. lol Knock on wood. I hope they remain that way. It makes being effective a lot easier with that kind of consistency.