First of all yes, it will be possible to accept Paypal payment through INR currency. Reference as below:
https://www.paypal-community.com/t5/Merchant-services-Archive/Receive-money-in-INR-curreccy/m-p/201016#M3429
Now, in magento to allow base currency to be INR, Override app/code/core/Mage/Paypal/Model/Config.php
Change:
protected $_supportedCurrencyCodes = array('AUD', 'CAD', 'CZK', 'DKK', 'EUR', 'HKD', 'HUF', 'ILS', 'JPY', 'MXN','NOK', 'NZD', 'PLN', 'GBP', 'SGD', 'SEK', 'CHF', 'USD', 'TWD', 'THB');
And add INR as below:
protected $_supportedCurrencyCodes = array('AUD', 'CAD', 'CZK', 'DKK', 'EUR', 'HKD', 'HUF', 'ILS', 'JPY', 'MXN','NOK', 'NZD', 'PLN', 'GBP', 'SGD', 'SEK', 'CHF', 'USD', 'TWD', 'THB','INR');