Wow, I'm impressed with your responsiveness, Zulf!
Great, how fast you solved this! This is a great addition, especially when one changes from the 3-featured-posts lay-out to the 4 one, the original featured links font seems totally oversized, so it's wonderful that we can adjust that now.
Another thing that I couldn't find (maybe it's there and I just overlooked it) is where to change the font size, type and color of the Tag-line. I did find the Site title font size and type under "Header", while the Site title font color is under "Colors", but the Tag line font size, type and color? If I may add a suggestion - I have no idea how much work this involves, but I think it would look really cool if the Site title font size and type moved from "Header" to "Site Title & Tagline" and the site title color likewise from "Colors" to "Site Title & Tagline", and then add the Tagline font size, type and color there too.
Another suggestion would be to add the possibility to get rid of either the Site Title or the Tag line, instead of keeping either both or removing both, as is the current setting. In previous Twenty lay-outs it made sense to couple both, but given the location of the Site Title and Tag line in Twenty Fourteen it could make sense to keep the Tagline without the Site Title, for example when one includes a header and logo above the menu bar then an image Site title can be placed right above the Tagline within the header, in which case the text Site Title becomes redundant. One may also choose for SEO reasons to keep the text tagline, even if the site title is an image within the header.