12V / 6A Power supply. Help with Buck and Boost converters + OR'ing circuit

Hello all.
Maybe someone here can give me suggestion of ICs and make considerations about this design.
The picture below states how this power supply should work.


Details:

1) IC 1 probably will be a LT3650-8.4 from Linear Technology. It supports up to 32V of input voltage (40V peak). Suggestions of other ICs for this purpose?

2) The power supply INPUT has only two states: (A) Floating (cut-off) and (B) 17 to 30VDC present at the input.

3) The OR'ing circuit at the OUTPUT, as the picture shows, doesn't mean it will be done with diodes. It can be done with MOSFETs, relays, or any kind of logic control like, for example: When the INPUT is connected to a 17 to 30VDC PSU, a logic LOW is present in an ENABLE pin of the BOOST converter, so that this remains in idle state (Output in high impedance). When there is no power supply connected at the INPUT, the same ENABLE pin goes logic HIGH, so the BOOST converter goes to active mode and presents 12V at its output.

4) The intention of using batteries is, case the INPUT be floating, maintain the circuit connected to the 12V OUTPUT working for at least 10 minutes (If more, better), through the BOOST converter

5) Which BUCK and BOOST controllers could I use for this design (IC 2 and IC 3)?

6) How can I do the Or'ing circuit between Buck and Boost controllers? Some suggestions?

7) There are no restrictions if heatsinks are required. No restrictions with the final physical dimensions of the PCB. Just need to work.

8) No problem if external MOSFETs are required, both on Buck and Boost converters

9) Final cost of this PSU is not so important.

10) Preference to SMD packages in all the circuit, if possible.

11) The 12V OUTPUT can be designed to deliver more than 6A. No problem about that.

12) No need of insulation (Flyback / forward topology, for example). The topology can be modified to Flyback / Forward also

Maybe a Power supply like this already exist in the market (a final product I mean), meeting this specifications, or even better than, ready to use. I did some research about but didn't found any models.

For the time, all I found is a Buck converter from Linear Technology, based on a LTC1624. Example of a 12V x 10A output with Vin range of 13 to 28V using this converter:


Somebody help me ?
Thanks in advance.