Yes, there is such a thing as solvent-free reaction systems. By performing a reaction "neat," you can eliminate any potential interference by the solvent on the reaction. You may also seek out a solvent-free system to remove a As you surmised, it can impact the kinetics of the reaction.
Homogeniety is achieved the same way for a solvent-free system as for a system with solvent--vigorous stirring.
I don't know how frequently industry uses solvent-free systems in production, but I've worked with quite a few in R&D.