Rough rider should have another disadvantage to focus playstyle more on mech.
“Barracks unit training times increased by +100%” or “+2 and +3 weapons upgrades at the engineering bay are unavailable”
Both of these would leave regular bio openings relatively unchanged while incentivizing players to transition into mech or hybrid mech during the mid/late game. The former would make it difficult to replace army (which happens mostly in the late game where splash is everywhere) while the latter would weaken bio damage while still allowing them to meat shield for mech units.
Justification for why rough rider needs disadvantage:
Currently, Rough rider is a straight-up buff. Afterburner attack speed is very potent to the point where the extra gas cost doesn’t really matter, and no one misses the 100% move speed bonus.
The prestige has 0 effect on mass bio+spider mine style (which is raynor’s “standard” build). So it buffs mech while having no downsides to bio. There is no reason to pick default raynor over this prestige.
The purpose (I assume) for this prestige is to promote more factory builds, but it does so in a way that doesn’t DISCOURAGE bio play. For boosting factory/starport play, its drawback should be weakening barracks units.