Artificial counterbalances like forced ratios never work out. They inevitably take away from strategic choice, and can cause more problems than they solve.
There are two issues with spam right now. The first is with low-tech units (Advent with seeker/disciple, primarily), the second is Advent illuminator spam. It's worth noting that there is effectively no spam problem from either the TEC or Vasari factions, it's all Advent. The only time TEC or Vasari players will spam is if their opponent is spamming to begin with and they're just massing the counter. This indicates the problem isn't wide-scale, but rather specific to a few units from the Advent faction. Illuminator spam in particular is due to a bug that causes illuminators to deal extra damage. Once that bug is dealt with, the illuminator spam issue should more or less resolve itself.
Now, as for low-tech units, there are great dangers associated with just "banning" spam like you suggest. Light frigate spam as an important role as the counter to a capital ship rush, and as a way to cover for a civic-lab opener. If you take away the ability to spam light frigates, you risk making certain capital ship rushes uncounterable or at very least overpowered. Secondly, you could completely kill off civic-lab openers because players will be forced to unlock high-tech units to actually build a large fleet. Here, people aren't spamming because these are necessarily the "best" unit types. They're spamming because they are cheap, reliable, and can be deployed quickly without having to wait on military labs.