railings were replaced with aluminum plates because these frigates will have some stealth capabilities, so the vessel is more difficult for radars and missiles to detect, and then you can not have railing due they give very much radar reflection, a single aluminium plate in angle will not.
yes, but you have entirely REMOVED the railing on the bow. that is not an good idea. also, by adding those extra light machine guns you will remove all the extra stealth enclosing railing adds.
When it comes to the cannon on the aft deck you'll get the ammunition delivered over the deck, and will save some ammunition in the gun, it will provide some limited applications, but the 74mm has the property that it can shoot down missiles.
first of all: it is an 76 mm. second: it has deck penetration. it can't be placed over there, unless you remove the hangar. no other options.
even if your idea worked: I wish the ones who deliver the ammo over the deck in mid-battle good luck. you need two men to carry the projectiles, and the gun can fire like...... 60 a minute or so? so you will need around 200 men constantly working to keep the gun working.
maybe you know something about the ship, but not about weapons and naval architecture in general, if I look at what you are drawing and saying.