Opening a non native file is great sure but don't you think it would be better if you could save this file directly to all common siemens PLM formats and as a bonus having the ability to convert to inventor or other file formats like solidworks, creo...etc. Also here make some subscriptions available like in catchbook.
It's all about making impressions. give the users the feeling they are not only important for you but you also spoil them to give them the ability to do something that no other CAD reseller would give them without paying serious dollars.
So give them the chance to convert and buy something without breaking the bank on the fly.