I like the designs, but I have to pipe up and say you're twisting canon if you introduce these weapons at the TL's you suggest. There is no Rapid Pulse Fusion Z Gun in canon at TL15. Canon is that rapid pulse weapons trail their single pulse predecessors by a TL or so.
So in previous Traveller editions it has been established that at TL15 there is a Rapid Pulse Fusion Y Gun. At TL14 there is a Rapid Pulse Fusion X Gun. Etc.
You take the lower performance in terms of range/penetration in order to get the rapid pulse autofire bonus. As a vehicle designer you decide if you want to take that option.
Just on the Trepida, it was a vehicle introduced in MegaTrav. There was no Trepida in Classic, instead the Imperium used what came to be known as the "Imperial Heavy Grav Tank" which was a bigger and more powerful vehicle. For unknown reasons DGP decided to introduce the Trepida/Astrin combo. Originally the artist (Rob Caswell) designed it at TL15. DGP decided to publish it at TL14, again for unknown reasons (maybe so it could be produced on more worlds?). They also put its introduction into service as being in the latter years of the 5FW. I see it really as a mass-produced "mobilisation" tank adopted during wartime - it isn't particularly good but was produced in the Marches to meet wartime needs.
In TNE's Regency Combat Vehicle Guide, Dave Nillsen tried to make sense of the Trepida and introduced some better variants, including one at TL15 (called the Norris IIRC). If you're really into Imperial combat vehicles I highly recommend obtaining that book, as it is detailed, well-thought out and useful to start designing equivalents in MGT2e.