If maximize their talent I can see they can in the future. However, to expect them to do it in near future, IMO the chance is slim. Let remember we're talking about team tactic where for most part we need to supply for Lukaku. Martial especially, is one at this stage of his development still a player who need supply than can work to supply others. His game is clearly of a forward where he prefers to spark into life closer to opposition goal. Rashford has the mentality which make him more adaptable for the position, but doesn't make him any close to good level winger. His dribbling is inconsistent, he can cross but at times doesn't have the instinct to time his cross. Sometimes too rush to cross, some other time miss first time cross chance doing circle dribbling.
I disagree with our wide players performing at high level than Perisic for recent time. They may have ceiling, but for each to maximize their game, other players usually would have to suffer much to the point that no one has any consistency with their form. Perisic the past few seasons, we're looking at the consistent level of Valencia. Not high enough or not, his level is assuring that it's less a problem in team balance to solve.
Lemar would be direct competition for Mata, Micky Lingard &a partially stifle Martial for game time. It's hard enough to get Martial & Rashford to consistent high level, and here you're more willing to go the long way with Mitchell he is further behind in development phase to solve big problem! Remember that Shaw was way way ahead of current Mitchell in development term, & yet Shaw is finding it hard to get there atm. Like the post I wrote in the transfer tweet, if you lose sight of the big picture as a whole club/team, you risk doing Arsenal: waiting too long for an internal development in one position, for another problem to pop up in a previous good position.
Can only be a good sign really, wouldn't complain, always trust Mourinho with signings.