Lots of great suggestions here. You might consider the advantages of fishing from the front seat -- only about 1/3 the ballast requirement (placed in the stern of course), better speed and handling, longer front cockpit (although narrower), easier to swing your rod across the bow. You can set the rear cockpit up as your cargo well and have good access to the bow hatch as well.
If you use water for ballast, you probably want to use it in the front cockpit, but not inside the hull (in case it leaks). If not the greatest for efficiency (requires more weight), it has the advantage of not having to carry it around! For those interested, the lead shot filled drivewell plug comes from Stringy, who uses it in combination with water bags. Here's one with a simple handle and a thinset slurry inside to stabilize the lead and plug. No reinforcing is necessary as long as the plug is in good shape:

This weighs about 24 lb and when locked in the front drivewell, has a very stabilizing effect.
If sitting in the bow, you can place this in the extreme stern through the aft hatch. For rear seat solo work, the accompanying 3" tube holds 31# of lead wheel weights melted in cans and sealed with more slurry -- stows in the extreme bow where it gains the best leverage, with the plug in the front drivewell.
Lots of possibilities. IMO, the Oasis (solo) can do everything the Revo 13 can and a lot more!
