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As iBGP normally runs across an IGP, and it generally converges slower, don't see many advantages using it alone. Even with an IGP, unless you have multiple eBGP routers, i.e. you want them to talk BGP between them on the LAN side, don't see many advantages for that either.
As to replacing EIGRP with OSPF, both very much alike in their major features to support most IGP needs. Perhaps biggest difference EIGRP does have some advantages over OSPF, OSPF is supported on non-Cisco.