I think I might have found a way to convert phylogenetic trees from image to nexus format through a process similar to that used in GIS map vectorization. This approach should also enable me to deal with trichotomies. The pattern matching approach that I had used previously turned out to be unsuccessful because of the many inconsistencies in tree drawing making it difficult to find a pattern that would always match a tip or a node. Line tracking offers hope!
All this would be so unnecessary if only researcher submitted their phylogenies to TREEBASE. Still, there are a number of phylogenies published prior to Treebase.