So when did GTVA need long legs exactly? Sol invasion, sure, don't send UEF stuff to Sol. Send something else. Use some of UEF craft for strategic attacks.
Going through the portal? Send something which will last a month in the wilderness. Fight hard for your life? Use better craft with better weapons, whichever those may be. They combined Vasudan technology with Terran. Decades on, they can't use UEF stuff? Hey, maybe those Hecates can finally be of some real use...
Consider this. The GTVA is in a war against an enemy with no known limit on ressources, with no known strategical vulnerabilities to exploit. In the long run, the GTVA will lose
, unless it can find something that substantially changes the equation. Until then, the GTVA's mandate is to ensure human/vasudan survival.
Now, Consider Sanctuary. Even in the "prime" universe, the Sanctuary plan was likely put into motion during the first incursion. They didn't go through with it, given how quickly the shivan threat evaporated after the Lucifer was shot down. That plan is still one of many contingencies in the GTVA playbook.
Further, take a look at the Anemoi class. Sure, they're incredibly useful. But they're assets geared for expeditionary warfare, something the GTVA actively discourages. Their capabilities are far beyond what a logistics vessel for a long-term patrol of known space would need.
Yes, there are obvious reasons why the GTVA favours endurance and ease of maintenance. Transparent ones for easy dissemination and consumption by the populace. However, there are also other reasons that people in the GTVA rarely talk about because noone wants to raise the specter of having to pack a couple thousand people into cryo and flee into the wilderness.