I'm incredibly unqualified to even think about how one might get faster random access times but i was imagining sci-fi solutions like looped tape so that you are always at most 1/2 of the tape length away from the point you want to reach, or the tape equivalent of multi actuator hard drives where there's be multiple independent tapes in one cassette in a sort of RAID style thing but maybe instead of (only) striping data could be stored on multiple tapes in different places to always have one tape that is at a position close to the data you want. Or a system where the same tape has multiple read heads applied to it in distant places.
That's of course true, i was just wondering how far we could push it.