Allies need to be incorporated into the standard FOC, without giving an additional slots to the user. The rest is good enough in my opinion (but then I play rarely and never in tournaments). Single FOC should be used up to 2500.
When it comes to Assault phase there is a LOT to be done:
Tone down assault distance randomness - a must in my opinion; 3-4+d6 should be good. You may risk and charge further, you may play cautiously, up to the player.
Make it once again possible to charge from a stationary vehicle.
Make it once again possible to charge from outflank. Appearing from outflank should look like that: move up to 2 inches from the edge of the board (or in a way that the whole vehicle fits on the board.
Make it possible to shoot overwatch at full bs for units that weren't shooting in the previous shooting phase.
Rework challenges shenanigans. Make it an option but not a game changing mechanic (model refusing challenge may fight normally but it's ld cannot be used for this combat round).
Those above were mandatory, those below are optional:
Give players freedom on how do they want to move to cc (making holding back and avoiding terrain allowed).
Rework Sweeping Advance, so it does not allow removing whole squads, omitting "to hit", "to wound" "armour save" mechanics. Make it work like a bonus round of combat for the winner without fighting back from the loser.
Make it possible to engage units in cc by consolidation move (with overwatch being included of course, combat being fought in the next assault phase without charge bonuses).
And I will repeat this one, incorporate 2+ and 6+ hits to "to hit" chart and add auto wounds for hits being over 2x stronger that target's toughness.
