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Personally I don't agree with setting internal filter URLs to nofollow.  I set noindex as you have done and add the filter attributes to the Search Console > Crawl > URL Parameters. For the option "Which URLs with this parameter should Googlebot crawl?" you can set "No URLs" (if the filters are uniform throughout the site). "No URLs: Googlebot won't crawl any URLs containing this parameter. This is useful if your site uses many parameters to filter content. For example, telling Googlebot not to crawl URLs with less significant parameters such as pricefromand priceto (likehttp://www.examples.com/search?category=shoe&brand=nike&color=red&size=5&pricefrom=10&priceto=1000) can prevent the unnecessary crawling of content already available from a page without those parameters (likehttp://www.examples.com/search?category=shoe&brand=nike&color=red&size=5)"

Thanks for your answer. So for you it's big bang. Google seems to use our alternate to index our mobile site and display our mobile URL in his SERP even if all our mobile pages are noindex, nofollow.

To make it a little less of a coin toss, if the responsive site is delivering an even better user experience than the mobile website, redirecting the subdomain could be a benefit. You'd want to have solid split testing data from uniform groups of users, but if the directions point to responsive over m.website.com it could make since to go with the responsive site as the sole experience.