If you take (for example) a 2 ton system with a TXV, then slow down the compressor to half speed with a VFD, you essentially have a 1 ton compressor in an otherwise 2 ton system. Yet it can be made to work just fine.
Over what range do typical TXVs operate over? In other words, if you continued to lower the capacity of the compressor, about when would the TXV fail to operate properly? (Assume lubrication problems were solved in some other way.)