If your data providers cannot produce a simple flat-file correctly and consistently then all hope might be lost...

If you want to make sure data is good before you even try loading it, ask them to start providing XML files with an accompanying XSD. The XSD defines the format of the XML file including elements, attributes, types, max lengths, default values, etc. A nice side benefit of XML is that element-order (i.e. elements map to database columns) is not important. Also, new elements can be added to the XML schema without breaking existing imports and you get all the nice benefits I mentioned about guaranteed valid file structure and data types.

Like I said though, if they cannot provide a simple flat-file properly then XML, XLSX, pretty much requesting anything else might be a lost cause. You may just want to build a very dynamic file loader that can deal with column-order and data-type problems gracefully. You can do this kind of dynamic loading in scripting languages like PowerShell or programming languages like C# (stand-alone or within SSIS) or even raw T-SQL with some surrounding command-line tools but whichever the technology you select you'll be doing a lot of custom coding to deal with the ground moving under your feet because your data providers are not competent at producing data files.

Best case is to start trying to manage the data providers, working with them more closely, and putting incentives and deterrents into place in an attempt to get them to improve their deliveries.