The nice thing about Suikoden 4 is that you can mess around with your party during the entire game (but well enough to get you through the other boss fights at least) since the training hall gives you an easy way to level characters up (granted this probably isn't a good alternative for those who don't want to fight more extra battles than they have to).

I don't think a tank is as necessary in Suiko4 as it was in say... Suiko3, in which a tank with a firefly rune was almost your best way of survival - especially in strategy battles.

Granted, general set-up for your party would probably comprise of two attackers (or attacker/all-rounder) and one magic user, except pure magic-users are a bit tiresome to bring along on regular battles, since their physical attacks are so weak. I did gallivant around with Jeanne and Viki both in my party for a while just for the heck of it though. The thing is you'll really have to keep switching characters around if you want to discover combo attacks.

Mao and Nao is fun if only to play the mint and mushroom ant armies. <3 Otherwise, if you're not a big magic-user you'll probably not have much use for them. I didn't use a single mushroom while I was playing the game.

Admittedly, I didn't play around as much with the characters during my first play through, as I was planning to do all that the second time around, except I got distracted by other games in the middle of my second game.

Q2: Those pearls are love. I just buy every single pearl and sell when the price in Mordo hits 8000-8500. And the Trading FAQ here (http://arcina.com/temp/tradepost_summary.txt). It tells you what to buy/sell in each city. It made my life a whole lot easier. I have price ranges (by city and by item) on separate sheets, but the range of where it's best to sell is always the same. (I am hoping of course, that these don't change per game.)