Full Party Development
Discussion here deals with a six person party balanced to include several races and professions.
 
I) Encumbrance: For a full party this usually does not become an issue until about midway into the game. Even then it is not so problematic if you have followed a plan of increasing the Strength attribute for those members it will be most beneficial for, such as those suited to melee combat. 

This is usually the time when your party gains access to several vendors who sell heavier armors and weapons. Be sensible in your purchase of items. Vendors restock items regularly but sometimes it can be in the party's best interest to purchase disposal items such as ammunition, potions, scrolls, and so forth in quantity. Particularly the better ammunition. Give each individual member a full compliment of ammo or at least what they can carry without becoming burdened. Place a fair supply in the party pack then stash the rest in chests and lockers in the area. Return for these caches as needed.

Once your party reaches these areas vendors are readily accessible so selling off unusable items more often is the best way to keep party encumbrance down. Some vendors do pay better than others but waiting to get to them may prove unwise if the party becomes over burdened. In this situation harbor the more expensive items and sell off the cheaper ones. In doing so you won't loose too much pocket change and you'll keep the party from suffering any of the detrimental effects of being over weight.
 
II) Gold & Items: There are many necessary and wonderful items your party will need or desire and it will be expensive. Including some one in a full party with the Alchemy skill will totally alleviate this problem as long as their creations are identifiable. Include professions that either use magic from the Divinity or Psionics spell book to gain the Identify Item spell or include a profession that has a bonus to the artifact skill. If no one can cast the spell then be certain at least one member trains the Artifacts skill. Usually some one of above average Intelligence is the best choice for the job.

Some additional methods are described in Section II of Solo Development.
 
III) Magic & Resistance:  See Section III of  Small Party Development since what is discussed there also applies to a full party.
 
IV) Experience & Leveling Up: In a full party the experience from combat is divided over all members thus they level up more slowly than a larger party. This is not necessarily a bad thing. Basically the party members have additional time to gain skill increases between levels. They do not normally advance to a point where their skills can not cope with the monsters spawning. Early in the game this may be an issue but it quickly balances itself out.

The one drawback is that since they level up more slowly than smaller parties or a solo character they may not gain as many expert skills through attribute increases. You will need to plan which of these expert skills will be the most beneficial to the individual as well as the party and develop attributes accordingly. Race choices at creation can also affect how many expert skills a character may achieve. Refer to the Need for Speed page for one example of reducing the demand on an attribute's development. 

The average number of expert skills you can reasonably expect each individual to attain by the end of a normal game is around two to three. More may be possible if certain races are used. (What is meant by normal is not the game difficulty level. Rather it means a party that just does what is needed to finish the game without spending any great amount of time "hunting.")
 
V) Party Formation:  Party formation issues usually have a workaround as far as protecting vulnerable party members. Dependent on just how many of them there are. Physical attack options however can become increasingly limited for a large party. Weapon choices will need to include a variety of attack ranges from close to ranged options. View the Party Formation basics.