Hello,

This is possible as now majority of know how is located in server, there is some controller function to get header structure and fields/content validation like parse_preview.

ir.import is a Transient Model defined in base import so it will be easier to modify it.

if you can prepare data format compatible with def load(self, cr, uid, fields, data, context=None) (a list of field and a list of list) of orm that is "mapped" by def do(self, cr, uid, id, fields, options, dryrun=False, context=None) of base_import it should work.

But it is quite a work. Maybe you should look to port community module that do advance import and already support XLS.