Hi Tilak,
It is very much possible. You can add field just by specifying data type, length without specifyng Info Object. It 'll reduce your efforts for developing new infoobjects if you can not use existing infoobjects or existing infoobjects doesn't serve your purpose. PFB...
Hope this 'll help you to come to conclusion. Please assign points for right/helpful answer/s.
Thanks & Regards,
Pradip