How to veganize and improve this cake recipe? I have the Build-a-bear cake pan from Williams-Sonoma. The cake recipe is as follows:


3 cups (470g) all-purpose flour
2 tsp baking powder
1 1/2 tsp salt
16 tbs (250g) unsalted butter
2 cups (500g) sugar
4 eggs
1 1/3 cups milk
1 1/2 tsp vanilla


Sift together dry ingredients; cream butter, sugar, eggs; combine milk+vanilla; add flour to butter mixture alternating with the milk.  Bake at 325F for 45-55 mins.

This cake made in a cake pan with two wells.  Each well is a vertical half of the seated teddy-bear.  When it is done you trim the cake with a knife then glue the halves together with icing.  This recipe makes a basic vanilla flavoured cake which is a bit on the dry side.  When it's slathered in mocha icing the dryness is ok but when I use fondant icing to decorate it's too dry overall.

This year I want to make a bear cake again, however there are two changes I need to make.  First, I'd like to make the cake moister without sacrificing its physical durability (it needs to be able to sit up without crumbling apart).  Second, I need to replace the milk, eggs, and butter with non-dairy/non-eggs because my new son is allergic to milk and eggs.  I'd ask two separate questions but I think they both need to be addressed at the same time.

How can I make this cake better tasting AND vegan?
To make it vegan is simple:


Replace the milk with any other kind of milk (soy, rice, hemp, etc.)
Replace butter with some kind of margarine (I recommend Earth Balance, but just pick anything that doesn't have trans fats)
Replace eggs with either commercial egg replacer, or apple sauce


As for making it moister, I have no idea.