It's quite do-able. First, in TechTree.xml, put

< Propulsion ID="TransWarp" >
< DisplayName >TransWarp< /DisplayName >
< Cost >5000< /Cost >
< Description >5,000 RP (AI:5)< /Description >
< Details >All ships gain +2 speed< /Details >
< Requires >HyperWarp III< /Requires >
< SpeedAbility >20< /SpeedAbility >
< Model >hyper320< /Model >
< AIValue >5< /AIValue >
< Category >Propulsion< /Category >
< /Propulsion >

Then, in GC2Types.xml, put

< Drive Name="TransWarp" >
< DisplayName >TransWarp Drive< /DisplayName >
< Description >Each engine provides 10 movement points< /Description >
< Cost >10< /Cost >
< Size >5< /Size >
< SizeMod >5< /SizeMod >
< Speed >10< /Speed >
< Model >Hyperwarp2< /Model >
< Category >Engine< /Category >
< Tech_Requirement >TransWarp< /Tech_Requirement >
< /Drive >

(Remove spaces after '<' and before '>')
Store both files in [WhereGameIsInstalled]\Mods\[yourmod]\Data

Now when you run GC2 with your mod enabled, TransWarp technology will appear at the end of the propulsion tech tree. Once you research it, all ships will get +2 speed boost, on top of the +1 for Impulse, +1 for Warp, and +1 for HyperWarp (total +5).

In the above example, TransWarp Drives are 10 movement points each. A ship with just one would get 10 plus it's starting +1, plus the +5 technology bonus, for a movement of 16. A ship with two of these engines would have a movement of 26.

In other words, ships with lots of TransWarp drives would be able to get just about anywhere in one turn -- the definition of transwarp.