The only offensive T1 land unit you will ever produce at T3 stage is arty, it takes 2 seconds to currently make a t1 arty with a t3 land fac. It takes 3 seconds for a t1 arty to leave a land factory. This is a sum total of 5 seconds. If you made it take one tenth of a second it would be 3.1 seconds per t1 arty or 38% faster.
A T3 support fac costs the equivalent of 6 t1 factories. Each factory takes 9 seconds to make an arty combined with 3 seconds of unloading time. This comes down to 2 seconds per t1 arty.
Even with this it's bad. Only exception to all of this is that it's a buff to zthuee amphibious spam, but zthuee was already intentionally adjusted to not be super spammable from few factories lol.