So you'd be happy only playing iOS F2P games and ports of Xbox 360/PS3 games then? Right now that's all Apple's GPU design is really capable of running and making a bigger one with more power won't actually change that. It is *remarkable* what Feral have done with Rome Total War and GRID Autosport on iOS - and DXMD is a much newer, more demanding title.
Mr Pink's suggestion could kill it stone dead.
A modern Deferred Renderer as used by all AAA Desktop/Console titles assumes that the GPU renders the whole frame directly to VRAM and that changing render-targets is cheap. These are properties of an Immediate-Mode GPU design like those from AMD, Nvidia & Intel. Apple's design is similar to the PowerVR designs it replaced in that it does not render the whole frame at once, instead saving silicon by rendering only a tiny sub-rect (a "Tile") at a time. This is called a Tiled-Binned-Deferred GPU design - they tend to be very power-efficient and therefore great for phones & tablets, but they make Deferred Rendering impractical (i.e. sub 10 fps). On a TBDR GPU rendering to an array of render-targets, which is required by Deferred Rendering, reduces the tile-size and that exponentially reduces rendering efficiency. TBDR GPUs must also flush all outstanding work to change render-targets in a much less efficient way than Immediate GPUs which can more naturally allow future vertex processing to overlap with outstanding rasterisation work (as they have *much* more memory and memory bandwidth). I haven't even mentioned the absence of any volumetric rendering support (so no lit-translucency, point-light shadows or atmospheric effects in UE4 on iOS!) or the absence of geometry shaders, or buffer writes from vertex-shaders etc. etc. etc. You get the picture - iOS GPUs lack a lot of the features of modern desktop GPUs. Adding them would be *hard* and you can't guarantee that Apple would.
And before anyone mentions the UE4 AR demo at WWDC 2017: I do all the Metal development at Epic, including this. We demonstrated the Desktop Forward Renderer originally developed for VR which is far less feature rich than our Deferred Renderer and doesn't require quite so many features that are unavailable (or fundamentally impossible) on the iOS GPU. Even then it was incredibly hard work to get it to an acceptable state and features were disabled that can't be done on iOS (lit translucency and atmospheric effects). It is not viable to expect any developer to retool each game engine & all game assets like this to run on both a Deferred Renderer for proper platforms (Windows, PS4, Xbox, AMD/Nvidia Macs) and a cut-down Forward Renderer for Mac & iOS with Apple's GPU. It can make sense if you are developing a low (or at least lower) end version for mobile (iOS/Android) and a high-end version for desktop, but probably only if you are the original developer - it'd be a huge undertaking for anyone after the fact.
Suffice it to say I think that it would be a huge mistake for Apple to adopt their current iOS GPU for Macs. Should they want to they would need to make considerable, fundamental, changes to make it a viable replacement for GPUs from AMD.
And with that I've derailed Ellie's thread enough. I will simply reiterate my congratulations on their breakthrough & progress on DXMD and hope there are more announcements to come!