The cheapest way to get a new calibre it to buy a new rifle. Modifying, sporteriseing or custom build all end up more expensive.

The Zastavas are cheap. I think POSS had one for sale. There was a special edition CZ 7x64 for sale at Cleavers not so long ago which would have been a great buy.

The only way to get everything you want is a custom build and any 8x57 Mauser '98 will do that with no work needed to feed. Mill the rear bridge flat and everything else basically bolts or screws on.

The ideal (for me) would be a small ring Mauser however my full size Mauser 98 was built up by Tony Small into a very light and handy rifle.

Good wood and adding 'stuff' to the barrel gets expensive. Alex will have a few actions that are suitable, maybe even a barreled action. Gordon Cummings/Cummins ?? is also in Tasmania and he bought most of the supply of Geoff Slee stocks so you could pick up a 'English Classic' style stock easily enough.