I'm also trying to do something similar, from what I can tell, it doesn't seem possible to use a mc:variant inside a mc:repeatable and have it work the way we want.
Using the following:
<div mc:repeatable="repeat-wrapper">
<h1>Repeat wrapper</h1>
<tr>
<td>
<div mc:repeatable="catsdogsbirdsfish"
mc:variant="meow meow meow!">
<h1>Meow!</h1>
Cats are the best!
</div>
<div mc:repeatable="catsdogsbirdsfish"
mc:variant="woof woof woof!">
<h1>Woof!</h1>
Dogs are the best!
</div>
<div mc:repeatable="catsdogsbirdsfish"
mc:variant="tweet tweet tweet!">
<h1>Tweet!</h1>
Birds are the best!
</div>
<div mc:repeatable="catsdogsbirdsfish"
mc:variant="glub glub glub!">
<h1>Glub?</h1>
I don't know what sounds fish make,
but they are the best!
</div>
</td>
<td><p>End of the repeating element</p></td>
</tr>
</div>
I could create and repeat any number of Cats, Dogs, Birds or Fish. The repeating UI appeared along with the variant dropdown selector. I could also create a new Repeat Wrapper but I could not insert any Cats, Dogs or Birds inside the newly repeated container :/