So I just finished the imperium campaign, had fun I must admit, however one of the most amazing things of BFG1 was the weaving of the plot through the turns with the amazing cinematics, epic moments like:
Which truly brought relief in the players when the gothic sector was under siege from every side and undermanned, where you had to strategically lose some words, then about halfway in the warp storm is gone and you can start re-conquering.
In the first game the lore, grim darkness and the struggle mankind faces in the setting is also told through interludes such as:
Then we have the boss fights, in both games they are honestly fine gameplay wise, however it's incredibly...boring? pointless in bfg2? We literally get 5 seconds cutscenes for each while in the first game it truly felt we dealt a final blow to our opponents whatever your choice was:
Finally, in BFG2 if I wasn't a fan of 40k before or I wasn't up to the 42k lore I wouldn't know who Roboute Guilliman is or why is he a big deal or why and how he came back, who is Trazyn and who is Cawl (who anyway was just seen once), honestly the Prologue was perfect, it told the player what Cadia was and why it was important and that's the kind of narration I expected from the rest of game and that we never got...
Not sure why, perhaps because they had to focus on 3 different factions? Still the world building and story of 40k is essential to make it a great single player experience and the first game had it just perfect.
Replays and observer mode are essential features for RTS, not only they help the players themselves to get better at the game and learn more from their mistakes but they also help immensely with the longevity of the game (and that also translate into more profit in the future for the developers) by creating a community centered around entertainment (many RTS channels show high level replays and get anywhere between thousands to hundreds of thousands of views) as well as a tool that more expert players can use to analyze the game balance and teach players how to play or how to get into the game.
So at the very least there should be a replay feature before the official release and later on an observer one, but replays are a MUST have.