It seemed like a good idea to put coat of paint on my city, so it doesn't look like Lego blocks anymore. Luckily I found a great free city tile pack by Kenney and here's the result
I also changed the mechanic of the HQ, after buying or renting office space, in addition to buying technical equipment, you can buy rooms for employees (tech teams, researchers etc..), which determines how many of that unit you can hire. You still need to hire them though. Later, employees will get grumpy if you place their office right next to a huge noisy teleswitch, so it will make sense to get separate buildings for each, which is more expensive.