Refinance / Assumption to take out spouse name from loan

I am an investor from Texas and have a few loans under both my wife and I's names. I realized that we could double our fannie mae allowed loans from 10 to 20 by doing 10 for each name.

I called my current lender and they stated that assumption form are not allowed for investor loans (Fannie Mae rules). She was not so helpfull and did not give me 100% confidence. She said the only option is to refinance, is that so?

I do not want to take cash out of the properties, just want to free 'more Fannie-Mae Slot', hence it seams silly to pay full closing cost for just 'removing a name'

Has anyone been in that situation?