This will give you align, but not font size. Font size would be pretty annoying, as it makes everything different sizes, one of the benefits of NodeBB is it's uniformed approach, one of the main reasons I'm glad to be rid of awful BBCode like [glow] etc.
To make nodebb more accessible for people with no knowledge of css it would be cool if themes could have options to customize colors or at the very least have a few preset theme colors.
selecting one of the options would change the whole color scheme of the theme, kinda like bootswatches for vanilla but added by theme makers.
vanilla and lavander are both kinda preset up for this with the use of variables.less
if you could add a way to select 1 of X amount of variable files you achieve this idea.
this would allow people to get more and easier mileage out of each theme, and help designers trying to make pay themes