There is no issue to use AbstractModel actually main purpose of the AbstractModel to satisfied this kind requirement where we do not need any kind of DB schema change but fetch data and manipulate data from the various models/tables.

There are lots of examples available where AbstractModel used, mostly for dynamic report generation where data fetch and manipulate from various objects.

AbstractModel name is quite missing leading. in general abstract class means you could not directly use it's just blueprinted and have to inherit for used it but in odoo you can use AbstractModel directly :)

Hello, 

https://www.odoo.com/documentation/12.0/webservices/odoo.html

​Try this link, it has example of how you can make PHP xmlrpc call in odoo. 

you will get to know there you can use model name on which you want to perform some operation. 

There small example of create partner in odoo.

$id = $models->execute_kw($db, $uid, $password,
    'res.partner', 'create',
    array(array('name'=>"New Partner")));