Really the key thing is if you want direct access to your photos don't use iphoto because of the way it catalogs you images.
Quite incorrect, really. If you want direct access to your Photo then iPhoto is ideal. What you're referring to is direct access to the files not the Photos.
The illustration I use is as follows: In my iTunes Library I have a file called 'Let_it_Be_The_Beatles.mp3'. So what is that, exactly? It's not the song. The Beatles never wrote an mp3. They wrote a tune and lyrics. They recorded it and a copy of that recording is stored in the mp3 file. So the file is just a container for the recording. That container is designed in a specific way attuned to the characteristics and requirements of the data. Hence, mp3.
Similarly, that Jpeg is not your photo, it's a container designed to hold that kind of data. iPhoto is all about the data and not about the container. So, regardless of where you choose to store the file, iPhoto will manage the photo, edit the photo, add metadata to the Photo but never touch the file. If you choose to export - unless you specifically choose to export the original - iPhoto will export the Photo into a new container - a new file containing the photo.
It's all about the Photo.
Regards
TD