1. make air units operate differently. For instance: assign an air unit to patrol and intercept at a certain area, attack shipping in a certain area, CAS, strategic bombers to attack enemy provinces (with something to bomb) without continous plotting them yourself, or have them al wiped out when not looking at a mayor concentration of fighters just moved there.
It is possible to let your bombers hinder another country, yet it takes a lot of time and attention away from human players.
2. Reworked amphibious landing. With HOI (1.06c I'm playing), you can drop your units at any point you like. In WW2, operation Overlord took considerate amounts of time, resources and planning before go-ahead. In HOI, you just assemble a strike force, drop it somewhere, build a convoy to supply, and release hell. If your intended beach is to crowded with enemies, you just ferry them a beach farther. This doesn't help for historic accuracy. Also, it makes the Axis players having to reinforce any beach area to a great strenght. In WW2 the Germans where able to deal out incredible damage with just a few lower quality divisions on the beaches of Normandy.
Perhaps there is a way to enforce the invading player designate a beach, that beach will cost IC's and has a build time like a unit, and when the 'beach unit' is build, it allows an amphibious assault on that area. This will repressent the time spend on training, recoinassance, obstacle clearing, etc. that preceded the actual sea-borne invasions. It could be worthwhile to let different beaches have different costs to build, reflecting the pressence of fortressess, climate, distance to supply port, etc.
3. Make subs / strategic warfare different. If it is to much to do programming wise, make it abstract (like in the board game Advanced third Reich). Now I find it extremely difficult and time consuming to plan a strategic effort at resources, either playing as Axis (subs in Atlantic) or Allies (strategic bombing over Germany).
4. Statistics!! After spending a near continous 48 hours at your PC playing for instance as Brittain, the only reward for your effort is a screen with the 3 sides, and there respective points total. I would like to see stats with Tech process bars, units destroyed, units build, etc. A bit like the Age of ... series.
5. In addtion to 4. I would like to see individual country performance to determine a game winner. Let's say the Allies won in points total in '47, it might be interesting to determine which of the allies relatively contributed most. Also, it could lead to Japan being the (relative) best player in such instance.
These points (4&5) make the game more interesting, as there will be more goals to achieve then just getting those victory points before '47.
6. Rework the Intelligence Ops. I've been playing HOI for quite a while, and still haven't got a clue what Intelligence Ops do, though there are still Techs to research in that area. Perhaps you could have more concrete affects, simulating the decoding of Enigma and the Japanese codes, so that the player having these Techs could be aware of positions of Fleets / Subs or Land Forces (as the battle for the Atlantic, the cracking of codes prior to Midway and the Russian awareness of Operation Citadelle (Kursk) made clear in the real WW2. Just make the subs / fleets / land forces show up in detail (depending on level of Intelligence Tech either accurate number of divisions (lvl1), type of divisions (lvl2), type of divisions and read out of unit (Soft Attack / Hard Attack, kind of Tanks, Leader/etc.) (lvl3) ) every once in a while when those techs are researched.
7. As mentioned earlier: a resource pool to replace the Supply slider. If you researched the tech for ie. Imp. Med. Tnks., you can set your supply slider to building those units, which in turn can be used to reinforce losses (thereby strengthening the unit) or can be used to create new div's. If you have enough PZIV's in your resource pool, it can be worthwhile to use them to strengthen your existing div's, or to use them to create new ones. Also, I would envisage a reduction in build time for Div's if enough Tanks/planes/ships for that type of unit are present in the supply pool.
It will ad some chalenging reource management for players (especially Germany and Russia) by having to choose to build up a reserve of 'older' tanks, or to wait untill superior types are accesible. Perhaps you could convert the Tech 'Tank Destroyer' and 'Assault Gun' to have benefits for the older types of Tanks in your supply depot, like in WW2 even the PZ38(t) was in service for the entire war, first as tank, later as a base for several Tank Destroyer platforms (I believe the Hetzer was a succesfull adaptation of that frame, combined with a L48 anti-tank gun).
