Converting combi boiler to system boiler

[WHPES]

Anyone done this? Have a customer wanting to change a system to thermal store with stove, solar etc. Existing combi boiler they want to use to drive the cyinder as a backup in emergencies. I guess I could just hook it up using the flow and return and disable the hot water side and controls but would it be better myself and the spark to strip it back to the shell and rebulid it as a gravity system boiler?

(yes I'm an engineer with a Masters and do know what I am doing before anyone asks)

 

[lame plumber]

why not just use the f&r as stated but leave the nearest hw draw off on the combi working, save on breaking it all down

 

[Bunker]

A bit out if my knowledge set but sounds interesting and doable. If you use the existing f&r then i guess you'll be relying on the diverter valve, can't see why that'd be a problem but I think Id rather extend the flow and stick a 3 port valve in there instead. Easier to wire into new controls and cheaper to repair/ replace.