The Ruger Ranch is definitely a great choice for a compact hunting rifle, and 300 BLK is a solid caliber choice for deer hunting. As for other rifles to consider, some popular options for hunting and sport shooting include the Remington 700, Winchester Model 70, and Savage 110. All of these rifles are available in various calibers, including .243, and can be customized and upgraded to suit your needs.
In terms of the red dot sight, it's definitely a good option for someone who is left eye dominant and right handed. Some popular red dot sights include the Trijicon MRO, Aimpoint PRO, and Vortex Venom,
Duck Life. You may also want to consider a magnified optic for longer-range shots.
As for building a WK 180 or similar, that could definitely be a fun project, but keep in mind that the WK 180 is restricted in Canada and requires a special license to own. You'll want to make sure you're familiar with all of the regulations and requirements before starting a build like that.