Caseta can certainly be used as a whole home lighting control solution, but there are a couple things to note.
1. The Smart Bridge has an RF range of 30 ft. in all directions. This roughly equates to a home of about 2500 to 3000 sq. ft. If you are able to centrally locate the Smart Bridge in your home and run an Ethernet connection back to your Wi-Fi router you will optimize the RF coverage. The more open concept your home is, the better.
2. The Smart Bridge has a maximum device limit of 50 and the bridge counts as 1 device. Every dimmer, switch, Pico remote and shade also count as a device so make sure you won't be exceeding 50 (or really 49) devices in your home. There's also a limit of 1 Smart Bridge per system. It is possible to have more than one Smart Bridge in your home but I wouldn't recommend doing that since you'll need to create a unique account for each bridge meaning you'll need to log out of one system and into another system to control the whole house, which would create a bad user experience.
In regards to your other comments, you can use Lutron wireless occupancy sensors with Caseta dimmer and switches in standalone mode, meaning they cannot be paired to the Smart Bridge or controlled from the app. I have several rooms in my home with Caseta dimmers and occupancy sensors and have no need to have them be controlled by the app. The rooms I use them in are my bathrooms, mud room and walk-in closets. I have no need to schedule the lights in these rooms or control them with the app since the sensors handle the automation for me. Just something to consider in your application.
Also, Caseta does not offer keypads like RadioRA 2 does, but you can use the Caseta 4-button Pico's which have a keypad looking aesthetic. The list of 4-button Pico's that work with Caseta can be found on this page,
http://www.casetawireless.com/Pages/ProProducts.aspx. You can also get the buttons custom engraved for an added charge.
Lastly, Caseta currently does not support fan speed controls, however, many people use the Caseta on/off switch to control ceiling fans. You won't be able to adjust the speed of the fan, but using the Caseta switch would allow you to control your fans from the app, schedule them to turn on/off at certain times and add them to scenes.
Hope this helps answer your questions. If not, please let me know.