As a avid Guard player since the 3rd war for Armageddon I'd love to see some of the old favor come back and fixing of some issues with in the Guard codex.
Wishlist:
Commissars go back to a 0-5 HQ Option instead of a 5th edition squad style upgrade (was always a horrible idea). Commissar leadership only come back into play AFTER the Leader is shot. One one that can replace the Company Commander as a Lord Commissar or be an IC
IG priest be brought into line with the Sisters Priest with one being able to be upgraded to replace Company Commander or be an IC
Techpriest get IC rule and one being able to be upgraded to replace the Company Commander or be an IC
Lord Solar Macharius!
Yarrik and Krell points cut in half
Creed get a slight drop in points
Straken get a 5 point bump
Orgyn get their points dropped by 10 pts, at least. They're over costed and under performing.
Stormtroopers go from 16-11 points each and be able to score if they achieve a certain objective assigned before the game. Allow a Valkyrie or Vendetta to be a Dedicated Transport
PBS changed that one can be upgraded to a Primus Psyker that can replace the Company Commander or be an IC. You can also attach individual Psykers to squads for buffing (think Warlocks)
Place Veteran squads under the Platoon structure and make them a 0-1 option
Cut heavy weapon and special weapons teams to 0-2 option each per Platoon
Make Penal troops a 10-20 man squads with options for heavy/special weapons.
Give Chimeras access to the Autocannon Turret
Allow Rough riders to always score and get T4. Allow them to forgo a turn of shooting to attach new hunting lance heads so they can charge again. Also allow them to a charge through attack similar in concept to DE Reavers
Bump Vendetta to 170 pt
Bump Valkyries to 110 pts (double a chimera)
Give both Sentinels access to Multi Meltas and heavy bolters.
Make Scout Sentinels Elites
Add Vultures
Add static artillery platforms
heavy weapons platoons
removing of Griffons from the HS section and placed in the elite section
Dropping the Executioner points to 170 and have the option of either 3 blasts or one large blasts both str 7 ap 2
Allow for hullmounted multi meltas and plasma cannons on the LR's
Now for Supplements:
Catachans! deerrrr!!!!
Elysians (I'd say 50/50 that it says FW only)
Tallarn
Steel Legion of Armageddon
DKoK will 99.9% stay FW only
In general other than the Vendetta there are a lot of units that point costed right or need to drop. Some moving of units and tweaking of rules would fix the bulk of the IG Codex current issues.
I'd love to a regimental system come back but I sadly doubt that would happen thanks to the Supplements Books now.