I said it before, but I'll say it again. When I play RTS games, I turtle. I can't help it; its just the way I play. I can't bring myself to not turtle. So why is that relevant? Well personally, I think that factions like the Warlords (not the Imperial Remnant in the Hunt for Zsinj, but the Warlords faction in other GC) and Hapes Consortium should both be playable because of my play style. So it may be a bit unbalanced and harder to play as them. To be honest, there is no way to make anything perfectly even and fair without the game getting dull, so add spice by making things interesting!
Hapes Consortium
I don't really like the Hapes Consortium lore-wise, but I think they should be playable because I would like to try playing as them. You may say that they are isolationist and shouldn't have the ability to be led by a player who would use their forces for conquest, but I think that they ought to be playable in at least one Galactic Conquest so someone like me could see what its like to be them. Besides, they seem to be a faction that the only people playing as them would be people emphasizing heavy defense over offense would play as. But again, players should be allowed to see what they're like. Maybe adding more to their defenses or smart maneuvers by Hapan players would increase their chances of survival.
Warlords
I love playing as the Pentastar Alignment because they have cool units, have aspects of the Galactic Empire that I love while not being (completely) evil, and are an Imperial splinter faction. However, I would like to play as the Warlords faction because I could have any ideology I want to back up my reasons to split from the Empire. Playing as the Warlords faction, you would feel like you don't have to follow some story to tell you how to run your empire, and you can rule your way.
Yes, I am aware that in the Hunt for Zsinj you can play as the Imperial Remnant representing Zsinj's Empire, where you just fight the New Republic. The thing is, I want to play as the Warlords in a GC where there is also the Imperial Remnant, New Republic, Hapes Consortium, Empire of the Hand, Pentastar Alignment, and Duskhan League. Well, maybe not the DL or EoTH necessarily, but you know what I mean. Besides, I like the color the Warlords are, and I'm not saying replace colors, just make the Warlord's faction playable. It doesn't need bells & whistles or new & interesting stuff. However, they will likely need a way to hold off IR, NR, and PA Super Star Destroyers that will obliterate anything in their paths. IIRC, Warlord Zsinj commanded a Sovereign-class Super Star Destroyer, and that will likely make things easier as far as defending Warlord territories go for players.
I don't quite expect this idea to be taken very well by people who don't want these changes to come to pass, as in the past I've had people chide me for suggesting allowing people to play as small countries in Supremacy 1914 in the general chat. If I seem somewhat defensive in the way I type, my experiences with people from that game probably just jaded my fill of criticism. Intelligent feedback is always welcome of course.