Working on vtiger crm as erp since more then 3 years. My skill set in vtiger as below.
Installation Vitger
Upgrading of vtiger versions.
Module creation.
Bug fixing in modules, layouts and quries.
Customization in modules, vlayout, QueryGenerator ect.
Creation of new picklist.
Understand the structure of DB of vtiger. (vtiger_crmentity,vtiger_tabs, vtiger_fields) etc
Import and Export of excel report in different modules.
Develope attendence system modules.
Developing logistic based vtiger erp system.
Working on api of vtiger erp system to get and send the data.
You can see review about vtiger work in profile.
I am ensure to bring all your requirements successfully in time. I am look forward to hear from you so as to take it forward.