Quite a few new tool Airfix kits offer Diarama options from open or closed canopies open or closed doors (See the beautiful Tiger Moth model.) to pose-able control surfaces, and open or closed bomb-bay doors. The Me 109E is the only one with the engine detail you mention but quite a few others while not purpossily having the engine exposed for inspection, could quite easily be made with the engine open. These are all radial engine aircraft namely the Swordfish, the Gladiator and the Dornier Do 17Z, some minor surgury might be required but it is do-able. If you do leave the Me 109E cowling open you'll need to add some machine guns. If you look back a bit on this forum I've posted photos of my 109E with the engine open, with added guns & detail, you might find it of interest.
Revell many years back did a Ju 88 with seperate engines ( Kit No # H-113.) although I've not made it I believe it's quite a fair model, and the engine detail adding an extra dimention to the kit.Personally I feel this is something Airfix should pursue, after all engines are included in many of their 48th and 25 th scale models and it is possiible in 72nd as they've proved with the Me 109. It's a pity Airfix didn't include an engine in their new tooling of the Ju 87B,s all it needed was one extra part to sit on top of the exhaust pieces.
Possibly the autimate Diarama 1/72 model with engine detail is the Roden Bristol FB 2 fighter of WW1. If you've never seen it try the Roden web site. I have one in my stash and every time I get it out it scares me and I put it back with a "maybe one day" murmur.
Remember we do this for fun John the Pom