Since you already have multiple devices which can be used as a wireless AP, I would say just get a basic
ONT, something like
Netlink GPON ont which is high featured ont which works in new technology GPON . As it is high quality product, company gives 3 year warranty.
www.crtindia.com
Please note that to use the telephone connection which comes with BSNL FTTH, you would need a ONT device which supports POTS / FXS port. Else you can get a SIP phone separately too, I think.