So, this is my suggestion of a rebalance for small arms:

As for single/quad mgs (non-aircraft)

As for light walkers

We would also need to move up/down some techs:

Also, I would add the “gauss weapons optimization” on the applied science techs group to increase their firepower.
But some would say, then why I would consider researching High Speed Machine gun if I can research Gas Powered Small arms? Well, because there is no applied techs for gas-powered arms and they would suffer an increase in IP cost, as for the following table:

This would slightly increase the cost of mid-late game machine guns and make spamming laser-based units harder, as you will have to plan and build ahead heavy industry.

Same idea as with the machine guns price rebalance.

This rebalance could get some tweaks once we test it in game (for that purpose, I would make a togglable option for “small arms rebalance” in the game settings) to increase/decrease price or make slight adjustments.
Let me know what do you guys think about this "rebalance" to make some useless techs than we have already in game useful