Well since the lvl 8 is all you actually need in the game i'd suggest giving it a 1% or 2% boost to all (base) speeds with each lvl. that way it no longer stays at lvl 8 and you can actualy do smthn with it ;)

the % increse is at your discretion ofc, but seeing as terrans need to research 3 types of propulsion it would be nice to get at least a general boost from 1 of the techs. Hance the Hyperspace Technology is the ideal candidate :)