Hi Prithivi Raj,
We did indeed install SAP GW and UI5 addon components to our PI stack - how this was done I am not sure as I am not a SAP Basis guy but I assume it was done using the standard tools.
'Strictly' we are not using the PI as a 'FES' as we are not using the Fiori launchpad nor fiori roles etc ... we are offering however SAPUI5 applications from PI towards our internal landscape and yes we are using SAP gateway on SAP PI to connect to the gateway components on the ECC backends .
As stated in one of the blogs ... using PI as a Fiori Frontend Server would not be recommended although I don't see any technical reason for not doing so ..
Kind Regards,
Steven