Send flat file feeds through Amazon Merchant Web Services

Question

we are creating an interface between an ERP solution and Amazon Seller Central. The interface is to use the Amazon MWS to upload new products to Amazon, i.e. the product is not yet "known" to Amazon and it should be added, as our customer is selling it. At the moment, our customer is using the Amazon-provided Excel templates, uploading them manually on the Seller Central web site.

We currently already have a similar solution that uses AMTU, but we want to rewrite this, so we don't have to rely on AMTU anymore.

Having read the documentation on the feed XSDs, I'm of course able to create the respective XML files and upload them through MWS. Out of curiousity, however, I also tried uploading a tab delimited flat file. This resulted in Amazon processing the file and returning a flat file that told me about success or errors.

My questions are:

1. Is it possible to use flat files instead of XML files to add/update/remove products to/from the Amazon product catalog even though they are, according to the docs, only meant to update the seller's listings (price, quantity available, etc.)?
2. Will this be a "permanent" feature? I mean: If I make my interface upload flat files, will I have to change it again in a few months - is there any known date when uploading flat files will be deprecated?