Technically yes...in the dev.exe, if you disable slot restrictions then you can have infinite ability upgrades (both titans and caps)....however this also applies to fleet supply and logistic slots and so it would be a very broken game...
In practice, no you cannot...you could mod titans so that 20 upgrades would "unlock everything" by reducing the number of upgrades and/or number of levels for each upgrade path, and you could do as drian suggested, which is to make each level require 0 experience...