It may seem contrarian but I don't recommend getting things ready beforehand. That's for when you're doing something new, you have to think about it, make decisions, and don't want to forget anything. It doesn't really save time. The key is having organized habits, so routine that it's no different from getting dressed and running out to the car. Bags are handy by the bed, also gloves, hat, and whatever else I might need weather-related. It takes about a minute to grab a shirt, slacks, socks, fold and roll them up and stuff in a bag. Bag, keys, wallet, phone, belt, access card - I run the mental checklist on the way out and a quick ABC check on the bike and go. This part is faster than when I drive, or even if I used other modes, because I don't need coffee before the bike ride.

Why can't you drop your packed bag into the panniers? It seems like you have a time sink there.

At work, from parking the bike to shower and change also takes me 10-15 minutes, depending on if I have to wait at the gym, so I can't really help there except to point out that it probably replaces at least some showers at home so it might not be extra time spent. I think you have some slack in the return pack-up, because changing time is 2.5 minutes max. From my desk, four floors down the stairs, change, out to the bike, load up and go is 7-8 minutes total.