WARNING!
I learned the hard way. I bought a pre-made Bot at the "Bot store" (...the "Bot Emporium"?) that had a Quality Level of 9, which of course cost more money than Bots with lower Quality Levels. However, I did not care for the way this Bot looked; so I paid the $100 to be able to "customize" the Bot using the Bot Workshop.
The ability to customize pre-made Bots is a great option. I really liked the new look I gave my Bot.
However, as it had taken me a good bit of "Sim time" to save up and buy a Level 9 Bot, I was quite horrified to discover that the quality of my Level 9 Bot had been reduced to Level 0 by the customizing process!
The only thing I can figure is that if you use the Bot Workshop to "Customize" a Bot, the quality level of the Bot will be reduced to the Level that equals your skill at building Bots. So, for example, I had zero skill at building Bots...and, therefore, when I customized my Level 9 Bot (using the Bot Workshop), the Quality Level of the Bot I was customizing was reduced from 9 to 0. If my skill level at building Bots had been at 4, I'm guessing that the quality of my Level 9 Bot would have been reduced to Level 4, to match my skill level. (Please keep this in mind if you customize Bots using the Bot Workshop!)
Also, while I don't know this to be true, I suspect this does not work the other way around. In other words, I imagine that if you customize a Level 4 Bot using the Bot Workshop, your Bot's quality level will not be raised to Level 8 if your skill level at building Bots is at Level 8.
The Sims games are pretty good at giving players various warnings before players commit to performing certain actions, like deleting a file. I'm very disappointed that players are not given any warning about the potentially serious consequences to Bot Quality when using the customization option at the Bot Workshop. Players Beware!