The Gothic genre is fascinating in its longevity, and there's so much more that can be done with literary data:
Using network analysis in conjunction with textual analysis, we might be able to establish the patterns of influence between authors and works. For instance, the preface of The Old English Baron acknowledges that it's the "literary offspring" of The Castle of Otranto, and several novels feature characters who are themselves fans of Ann Radcliffe. Many chapbooks were just abridged versions of much longer three-volume novels - perhaps there were some that were copied more than others.
Character names could also indicate patterns of influence: reading through Tracy's summaries, there are a surprising number of novels who feature characters named Matilda or Theodore (both of whom are main characters in Otranto). Additionally, some names developed specific connotations - if a character named "Ambrosio" shows up, he's probably going to be a monk with issues...
In The Gothic: A Very Short Introduction, Nick Groom writes, "The crucial activity of the Gothic imagination was seen as inspiring terror and power, which was accomplished by creating sublime effects based on Burke's Philosophical Enquiry. The sublime signals the limits of rationality -- the 'sleep' of reason -- and was best communicated by obscurity" (p. 77) that ultimately serve "probe the consequences of history and telling of secrets" (p. 78).
Groom proposes an alternative recipe for a gothic novel, classifying the various motifs into seven categories:
A future project might involve restructuring Tracy's motif index to fit within these seven categories, thereby reinterpreting the corpus through Groom's perspective without having to repeat the data gathering process (i.e. reading through hundreds of stories).
Finally, researchers could continue Tracy's work through later periods of Gothic literature, gathering data on which motifs were carried on through the late 19th century, as well which motifs emerged as a result of sweeping societal change (i.e. Industrial Revolution Gothic). Will there be a new form of Gothic in the 21st century as a response to environmental change and governmental unease? Who can say?