Gian-Reto:
I see what you mean. I was actually perusing another topic that mentioned using client simulation that's verified and updated by the server. You're right about the pitfalls of using such a method (as I read), because it might cause a jump from one position to another. Just so we're on the same page, which part of my implementation would introduce that sort of lag? After considering all the previous replies, I'm leaning toward creating two gameplay modes: the battle mode and the freeroam mode. The latter is the only one in which real-time inputs would be handled by the server (such as walking through a town, or buying items from a shop). When a battle is triggered, the gameplay will change to turn-based, using timers implemented by the server. Are you referring to that portion of the game, or a real-time battle system?
I've never played Disgaea before, but I've watched Let's Plays of it. Since you've actually played it before, would you prefer that sort of gameplay in battles or the Mystery Dungeon gameplay. Both are turn-based, but I think the main difference is that one changes screens and the other doesn't. Stella Deus is another cool example of turn-based gameplay. Again, I haven't played it myself. Is it weird what I like watching Let's Plays?
I was referring to the idea of having realtime battles being networked with the method you described above (which omitted any prediction routine, so I though you wanted to go with the most direct way to implement it (delay client action until the action is verified by the server))... as said, the same problems are not as evident in a turnbased approach, as the player does not "feel" the lag as much (as he lacks direct control over his characters).
Control during the overworld sequences is much easier, as it is MOSTLY a one player expierience, with the other players mostly being a sidenote (they might be visible and move around in your client, but it doesn't matter much if their actions are synched with yours, as there will most probably be no collisions between player characters (to prevent griefing), and no way to interact other than chatting).
You will still need to verify things on the server (to prevent cheating players from walking through walls or buying in the shop without paying), but don't have to work as hard because pacing on the overwolrd map usually is slower, and correcting a prediction will look less off (if the player needs to be reset to a position because he tricked the prediction routine into not recognizing the wall and letting the player walk into the wall, you could do that in away that is hardly noticable (how fart into the wall can a character walk in a second?), or maybe even use an animation to hide the fact you are moving the character back (the "hit the head on a wall" animation)... you could even instruct the client to not let the player walk into the same direction as long as he doesn't move from the spot to temporarily harden the prediction routine against cheating).
Cannot really talk about the mystery dungeon series. The Disgea games are quite similar to the Vandal Hearts series from the battle system, and it is a system that is much more akin to chess than classical pen and paper RPGs.
Because your characters move on a map, have a set move and attack distance, positioning becomes the most important factor in battles, more important than slight level differences between opponents. Position in a way so you can strike first, and even better, you can strike with more characters against fewer, and you usually win. Make a mistake, underestimate the AI, and your lone character will be butchered by multiple enemies, even if they are low level grunts.
What I really liked about Makai Kingdoms was how it added vehicles (tanks for example) to give the player further options. Vehhicles usually had more range and superior armour and weaponry, but you only had like one of them, and they needed to be boarded by a character to work. The other Disgea games have mounts as a similar concept.
There is a clear skill component to the battle system, and that is mostly tactical thinking. The hit / damage / evade rolls might still be random like in usual RPGs, but to win a fight you had to utilize some simple yet important strategies concerning positioning. And because positioning is so important, the battlefield itself becomes important. Depending on the terrain and obstacles in the way, you could use the terrain to your advantage, while also needing to make sure to pick the right route for the right character so they would be able to attack the same enemy in the same turn.
Also, because of the alternate activation, you always had to be careful when attacking enemies that weren't activated yet. Setting up three or so of you characters to attack, moving in with your first character to do the first third of the damage to kill that enemy, only to have it move out of harms way before the other two could attack is a sure way to waste two of your characters damage potential for a turn. And depending on how well the AI is written, you might not get a second chance, as the enemy might now be in range of his buddies, and any of your characters that reach him next turn will get stomped by the superior force.