Hey Taylor,
You can re-assign. The ideal situation, which I believe I heard you can do but cannot find out how, is un-assign a Lead so that they are a free agent and re-run them through your auto-assignment rules. I would ask support how to do that. Then your flow would be un-assign, then sync to SFDC using the Auto-Assignement rules that take into consideration Revenue and Company size, right?
The much longer version is you could create a trigger campaign that looks at those fields (Revenue and Employees) whenever they are updated. Then, in your flow, you can add the Change Owner flow step and use the contstraints to act like the assignment rules. For example, if you do things geographically, If: State is: CA, AZ, NV, Owner Name: Taylor M. Obviously, the down side to this is that you have to break it down per rep and update if anyone joins/leaves the company manually.
I am pretty sure you can strip a lead of it's acquisition, but I would ask support. In the meantime, I will create a discussion about it to see if anyone else knows because this is bugging me.