so here the thing, by the time i have fabrication researched i already have the biotech bots, modded biotech bots, or colonist that make the tier one and tier two robots a footnote, unless i started the game with them or got lucky with a caravan they are gated behind too much research, and take way too much to research

so my suggestion, the robotic workbench research requirement is reduced from fabrication to eletricity, and the robots have 200 each to research(omni 500 + 500 for each tier update)
also researching them dont unlock all the robot bases, you unlock them as you unlock the chips to make them, so they dont clutter much

tier one robots(500) : just require the robotic workbench research, this way you can make some roombas and delivery bots early and if your in a pinch you can get the crafter bot t1 and put him in a stonecutter room to chizel blocks

tier 2 bots(500): require machining, at this point you would have a infrastructure to support them

tier 3 bots(1000): require microeletronics

tier 4 bots(2000): require multi analizer

tier 5 bots(2500): requires fabrication