One of the problems is single runway airports without parallel taxiways so aircraft have to taxi down the active runway - LTN & LCY come to mind but there must be many other examples.
Before parental bankruptcy forced my employer's closure three years ago, my civil and structural engineering colleagues were working on a further major upgrade to facilities at London City, including decking over the dock to carry a full length taxiway. This work was successfully handed on to another consultancy to complete (think my some of my colleagues transferred too) and looking at Google maps, the decking is being constructed so presumably it won't be too long before the taxiway is in use.