do you want a tapped GBB or an AEG conversion?
the former is easy, purchase your preferred GBB Mp7 and fit hpa valves to all the mags.
the latter i'm not so sure about, i've not seen the gearbox internals on the aeg mp7's but most of the hpa kits require a standard sized cylinder to drop into.
looking into it the VFC mp7 claims to be a full aeg, although looks like a shorter than normal cylinder with an offset cylinder. probably not impossible but i suspect it'll need either heavy gearbox modification or some 3-D printing to fit the usual suspects from polarstar/wolverine in.