- Allow queuing units for repair bay (TD) (looks like you have this planned already)
- Give harvester SelfHeal=yes to 50%, like RA1/TS/RA2 (TD)

- Allow APC to unload infantry all at once like RA1, rather than one at at time (TD)
There also seems to be an issue unloading APC's when at the very top and bottom edges of the map

- Make it so you can't build off of walls/sandbag like RA1 (TD)

- Make it so AI will destroy your walls, so you can't just build up into their base and trap them in (TD) (This is mostly resolved by the above fix, but could still pose an issue, for when you capture a building within an enemy base and do it that way).

- Personally I think infantry should take damage in Tiberium at all times, not just when they're moving, doesn't make sense. (TD)

- Allow harvester to be selectable, when unloading Tiberium in refinery (currently it merges with the building and become unelectable. Especially annoying if refinery is under attack and you want to save your harvester by moving it away. (TD)

- Change newly added 'Double click unit to select same type' to simply keyboard shortcut 'T', like later games TS/RA2. This will stop it interfering with unloading chinook/APC

- Fix SAM Sites so they don't pop up and down constantly, instead of staying fixed on target

- Having a 'Multi Engineer' option, at the start of skirmish, I think would be a great feature. So engineers function like RA1. This option was added exactly like this, in a later patch for Tiberian Sun.

Modern wall building
The TS + RA2 system had some downsides, to resolve these, I'd suggest, having it a
drag+build function

This means that:

- You will be properly charged for each wall segment
- You will be able to sell each wall segment and get a proper value for it
- You won't unintentionally end up connecting other walls together that are in proximity, then having to sell all the redundant wall segments