Your stainless steel cover for front is good idea. I have 23 gage steel roofing cut to fit my Kobo touch reader. I taped sharpe edges with plastic electical tape. Originaly it fit inside silicone rubber sleeve to protect front screen from breaking. Not recomended but I carried it in loose fit frount jeans pocket at ammusment park so I could read wile in line and rode rides including roller coasters. It is now slipped into inside cover pocket of leather book style cover. You need to protect screen from pressure and prevent twisting Kobo reader while in back pack or suitcase. Wood, or steel box is excelent or even good plastic box could work. Most use ready made covers with good results with reasonable care to prevent damage.
I think Pinch zoom is possable for all Kobo IR touch readers but only kobo eink reader that with it is Kobo 6 inch screen Kobo Aura with capasitive touch screen. These links should lead you to posts about installing pinch zoom.
https://www.mobileread.com/forums/forumdisplay.php?f=247
https://www.mobileread.com/forums/sho...d.php?t=217160