As far as I know, there isn't any company still making linear grey switch keyboard are they?
There has never been one AFAIK, except some limited editions, custom orders or whatever. Greys (and greens) are originally *spacebar* switches.
In regards to the OP, I don't see the point. Typing is a different experience from pressing individual switches, especially if you have to hold stabilized modifiers from time to time, and both feel and sound are affected not only by mounting, but keycaps and the user (mood, time, setting/environment) as well. Moreover, different kinds of keys usually require some getting used to. Get a PCB-mounted keyboard and some harvested switches/stems&springs and keycaps instead, and play with that a bit.