[Suicide Junkie]

I haven't played enough proportions to help, sorry.

Some mods restore some uses and effectiveness to smaller ships, though. See Proportions mod and AIC mod for example (and probably P&N and Adamant, I would guess - any mod with Quasi-Newtonian Propulsion will help at least somewhat).

The new SJmod has a unique system for ship value...
The little ships get you way more bang for your construction buck, but the maintenance costs on all ships are about the same.
The 400kt "Frigates" are pretty good for quickly mustering up some cannon fodder, or 200kt "Escorts" if you have a lot of slower BSY.
With construction time rising proportional to size cubed, 800kt of 1000kt ships are probably the best you can hope for in your main lines.
However, if you have lots of time on your hands, the biggest ships are the best, since every ship costs about 1000 in maintenance (scaled to stock-minerals) no matter what size it is.