Route-specific image is specific to the route. it does not matter whether it's your main base or another.
Company-wide image is global to the company. it does not matter whether you have 1 base or 10.
Marketing associated with those levels - route & company - stay at their level.
There is neither base-specific image, nor base-specific marketing.
So, to answer your final question, you need(if you feel the need) to use route marketing for any new route - wether the route is at a new base or an old one. And you don't need to change anything at your company-wide marketing(unless you find your CI too low for a company of your caliber, but try not to exceed 10% of expenses in marketing).
Or you can just wait 1 year for the RI to reach its maximum, and not spend any dollar. Your choice.