Yule Log -can anyone give me some specific help?

I'm baking for my christmas party the 21st.  Something like 50 people.  I usually make one or two christmas log cakes, large, about 13 inches long, pretty thick, and with two branches made the same way, but from a sponge baked in a smaller pan. 

I have two problems.  While everyone oohs and aahs about them, and they always eat it, personally I find them pretty dull eating.  It's for my own satisfaction that i do all this anyway, so i want to be able to enjoy it!

I have tried the following

cake:

1. sponge cake (6 eggs, 1 cup sugar, 1 cup flour) whether white or chocolate (cocoa replacing part of the flour) depending on the color of the filling, i like to make it contrast so the slices and the ends look like the rings of the tree. 
2. genoise

I didn;t see essentially any difference between them.  Both are dry and rubbery. 

filling:

1. chocolate or vanilla italian meringue buttercream 
2. white chocolate cream cheese buttercream
3. light whipped ganache

I found them all too rich

frosting

1. butter and dark chocolate ganache,
2. dark chocolate ganache (both ganaches applied fairly thick so i could make a bark effect using the point of a sharp knife pressed all over the surface)
3. simple italian meringue (no butter) (this was an additional cake, made to look like birch, with melted chocolate applied with the edge of a knife at various places along the bark)

These were also rich (except the meringue) but i don;t mind that, people even peel it off. 

my assessment:

They all look spectacular.  I stick small branches of bay into the log to look like the pieces of tree that remain when they cut a real yule log.  No problem there.  Also the birch log is extremely realistic.

However the cakes are dry or rather rubbery and uninteresting and the fillings are too rich after a huge meal and along with trays of maybe 8 or 9 types of cookies and a large (moist) fruitcake. 

My questions

1. can I use a buttercake recipe without it cracking when it's rolled out (it's a big pan, the short side is 13 inches)?  Can I use any butter cake recipe or do i need a special one and are there any special techniques?  Spongecake and genoise are rubbery so they;re easy to roll wihtout cracking, but it's the rubberiness i hate. I don't like liqueurs in my cakes so I'm not going to soak the cake with it.  I also am not a fan of cake soaked in syrups. 
2. what alternate sort of filling could I use?  I usually keep the filled roll in the freezer and take it out the day of the party so it stays cold at room temperature.   I thought of whipped cream - if i freeze it and then take it out will it work?  will it soak the cake in liquid as it defrosts?  What about half whipped cream and half italian meringue?  That could even be kept frozen since it stays soft?  With that i wouldn't mind the sponge cake so much.  Has anyone used whipped cream in a sponge roll and had it come out ok?  or whipped cream and italian meringue in equal parts.

thanks

Thanks for the suggestions

I've tried adding butter to spongecake before, and was not much impressed, but might try yours chefross.  Nutella, no, I used to like it till they made everything with it, and it seems most pastry shops no longer know how to make chocolate filling!  Also it's rich like all the other things.    But the pastry cream with whipped cream and gelatin (bavarian cream) might be just right.  Does it freeze well though? 

Koukouvagia, i did do a white chocolate cream cheese filling, but i felt it was too rich. 

Same for those who mentioned buttercreams. 

Ishbel, I didn't think of flourless sponge.  Interesting idea, should be moist. 

I'll try it out Ishbel. 

thanks

Well, i had my party and made my yule log.  As often happens, just discussing with you guys gives me ideas and gets me thinking, and i made the absolutely best (and i think nicest looking) yule log ever. 

I used a simple sponge cake (6 eggs, separated, 1 cup sugar, 1 cup flour, pinch salt, some vanilla) for the main part and the same but replacing more than half the flour with cocoa - so that i could serve one or the other, depending on the person's taste. 

I filled it with a mixture of whipped cream and italian meringue.  I froze it, and i figured it could be served frozen or defrosted, since it;s like ice cream. 

I frosted it with a dark ganache of 72% bittersweet chocolate and cream. 

The branches are laurel (bay) which i buy to make garlands and keep some for decorating the log. 

here is my picture (plus an english christmas cake (with the flowers - very moist) and a couple of trays of cookies. 

Happy Yule to you all

prettycake - can you give me the recipe for your rollable cake?