If anybody here plays ranked or custom 1v1s, you've seen T1 spam. It happens a lot. Pro players, on maps that are large or open, make obscene amounts of tech 1 land factories an ridiculous amount of tech 1 land units. As an example of this, in a recent ranked game on Open Palms, Voodoo built 22 tech 1 land factories and, at one point, had over 600 tech 1 tanks to bare against his opponent, TAG_PEBBLE, who only lost because he has fewer tech 1 factories and, as a direct result, fewer tech 1 units.
We all know that tech 2 and tech 3 units are more efficient than tech 1 units, and can utterly crush them. We also know that tech 1 engineers, which are used to make tech 2 and tech 3 units, are more efficient (per mass cost) than tech 1 land factories at building units. So what's the problem? Why do we still see ridiculous numbers of land factories and ludicrous amounts of tech 1 unit spam?
Thew answer is simple: Because 1 T1 engineer has similar build time to a T1 land factory, of 260 to 300.
What does this mean? How does this influence tech 1 land spam?
It's actually very simple. Assuming a pro has just started playing a 1v1 on a large, open map against another pro. Making units quickly and efficiently will be a deciding factor in map control, resource collection, intelligence collection, and eventually the game. So the player decides that he needs to make a lot of units very quickly. His openning build order has provided him with 1 tech 1 land factory and 4 tech 1 engineers, a total of 40 build power (20 from the land factory and 5 from each engineer). What is the best way to increase build power?
If the engineers assist the land factory in building additional engineers, it will produce build power at a rate of 1 build power every 6.5 seconds. However, if the engineers produce land factories (and the land factory switches over to making units) the player will gave 1 build power every 0.75 seconds. Building factories is slightly less efficient, mass-wise, than building engineers as a means of gaining build power, but it is MUCH, MUCH faster by nearly a whole order of magnitude.
Although T1 engineers can build tech 2 and tech 3 units, tech 1 land factories cannot, so players forced into massive tech 1 spam as the only viable method of building an army quickly. Tech 1 land factories offer 1 build power for only 15 build time, whereas T1 engineers offer 1 build power for 52 build time. Tech 1 land factories are, therefore, roughly 350% faster than tech 1 engineers.
So, what can change this?
The first idea is simple: Reduce the build time of tech 1 engineers by a factor of 4, from 260 to 65. This would allow a player to build 1 build power of T1 engineer in only 13 build time, which is about 12% faster than the land factory, and sufficient to put them into parity with each other.
The second idea is more complex: Allow T1 land factories to directly assist T2 and T3 factories. If T1 land factories were not limited to producing exclusively tech 1 units, most the huge benefit to spamming T1 land units all game long would be eliminated.
The third idea is more complex still: Give factories adjacency bonuses to other factories. Adjacency can take two forms, set bonus and percentage modifier. With a set bonus of -10 and a percentage modifier of +50%, tech 1 land factories would not give bonuses to each other (+50% of 20 mods it to 30, -10 brings it back to 20) but they would give bonuses to higher tech factories: A T2 factory (base 40 build power) with 4 adjacent T1 factories would have the effective build rate of 80, or +100% versus what it has now. A T3 factory (base 60 build power) would have 140 build power, +150% versus what it has now.
The fourth idea is one I've mentioned before: Halve all factory build rates (build power) and halve all unit build times (ones that are built from factories)