[satistaspawn]

Making all the effects permanent may reduce the range of possibilities, maybe any temporary changes when they are removed your character doesn't quite return to her normal self allowing a slow process throughout the game while still experiencing faster and more obvious changes while your playing. You may want to include quests where you are asked to retrieve item that will cause a temporary change when in your inventory that would also impede your movement forcing you to take an alternate route from the one you came because you no longer fit. Design the game with enemies that have powers that make you grow for a short time slowing you down and making you less agile or have the effects last until you can use a specific medicine/potion or visit a "healer"

Also if the effects are only focused around breast size it will feel a little repetitive after a long period of play. I'm not saying you have to go down the road of furry transformations but you can effect the firmness of the characters breasts and lactation, a nice big round bottom isn't bad either; longer legs and hair, a waist line ranging from curiously thin to almost full term pregnant, if there any harm doing something like and item when equipped gives kitty ears and a tail to give the character heightened senses in order to locate a missing person or item, maybe a spell for wings to get airborne in a certain area.

You could give the player the ability to learn how to effect other characters in the game but be careful cause they wont be very happy with you afterward. as the game gets further along you may want to use items to keep your size down and you abilities up, because the larger you are the harder it is to sneak and you way more so you speed and the height of you jumps aren't impressive at all and being as big as you are, you make an easy target for your opponents.