Actually you may very well convert shoes to cloth and change layer to available cloth layer slots. After applying shoes, just click "Transfer Skin Weight" and select "Other".
"Other" makes/retains a perfect weight transfer and converts shoes to cloth. The only thing you would probably worry about, is to have the same types of shoes applied (in relation to floor contact).
Having different types of shoe mix (high heels and boots for instance), may, or may not pose a problem in the destination app. You have to figure that out...

Here she is wearing 3 pairs of boots. And they fit perfectly regarding weights.