[Imp]

Don't commit the cardianl sin if you are going to mod it think about it & produce something thats a bit diffrent. Music covering someone elses song is the cardinal sin unless you put your own spin on it whats the point.
To do this you either have to do loads of tests or read to grasp the basics like what does ERA actually stop?
Simple things future tech better targeting why not set to hit to 150% in the prefs.
Diffrent weapons maybe something that hits big but has major range restrictions 3-9 hexes only. APCR could be set up to deal huge damage but have a very short range to represent burst fire up close or something.
Your bike infantry question they are more fragile generally but you could use these guys to represent poor battle armour because of that. Loads of other ideas these just come to mind without thinking about it think outside the box.