I will try to sugest tiny changes to ERE roster (that may be apllied to WRE as well) ussing basic material from the vanilla game.
1st NO PIKES!
So no Menaulatoi pikemen PLEASE!!!!!!
Lets start:
1: Limitanei Borderguards must have no body armor.
Based on this consept:


2: A version of them with two heavy javelins must be Exploratores (scouts on foot).
3: The scout equites must rename to Exploratores Equites.
4: Sagitarii remain as are.
5: Sagitarii Legiones replace Sagitarii.
6: Preaventores use the vanilla armor but are ellite ambushers (skill for hiding). As ellite unit must be available but in high prices!
7: Levis armature continue with downgrading stats and recruitment costs and time.
8: Lanciarii Minores (ussing the vanilla Exploratores consept) but with 4 javelins and sword.
9: Menaulatoi are the heaviest javelinears (with stakes placement abillity if possible) and replace or co exist as better version of Lanciarii minores.
10: Lanciarii Legiones replace or co exist as better version of Limitanei
11: Lanciarii Seniores replace or co exist as better version of Lanciarii Legiones
12: Cohorts remain.
13: Legiones are Legio renamed.
14: Legiones Seniores replace or co exist as better version of Legiones
15: Equites Limitanei (melee cavalry) with leather breastplates .. as link to the cavalry equipted with chain mail. That remain as is.


Ellite troops:
16: Legio Comitatences
17: Lanciarii Comitatences

18: Excuvitores must be guards only for the Emperor and Heir!
19: Vucelarii replace Tagmata horsemen ussing this concept:

Average armor but very affective against horsemen and very accurate as archers.
Very expensive.
20: Finally addition of Lithovolos catapeltes for ERE ussing Rome II's Roman Ballista.
The device must be more accurate and with longer range than onagers.
Must be 3 times more expensive though.
21: Units like Palatina, Palatina Seniores (or other name), Protectores Domestici and Scolae Palatinae must be only guarisson units based on the level of Governor's Pallace.
If possible can be scripted to Governors guarisson ...Not generals ones.
Generals must have Comes guards from the start and according to the skill or rank (scipt) must be able to recieve Magister Millitum guards.
22: Imperial troops.
Cataphractarii remain as are.
Clibanarii remain as are.
Numeroi remain as are.
Auxilia Palatina remain as are.
Added Sagitarii Palatina.

If someone with scripting expirience wishes something more complicated i can help with some basic ideas.
I hope ships can be modified too...