I was planning a while back to just remove the Gravebringer and use its graphics for the Mobile Infantry. Shall I proceed with that?
Yes, please! I think that would help a lot.
What would those extra units do though, keeping in mind they can already be specialized with special abilities?
Mainly because the special abilities are pretty encompassing - but not universal. In my opinion, they rather "round out" units - you pick them to either reduce certain weaknesses or increase their effectiveness in their specialisation - both are valid choices. It's nice to have choices like: Do I build cruisers and trick out their air-defenses or do I rather throw in some air-defense foils (let's say they have an in-built bonus against air) and improve the cruiser's defence against other ships? Or do I improve the speed of my infantry or do I combine them with other fast units and specialise their strength against native life?
That's a difficult issue. In vanilla Civ4 being a unit level behind is very dangerous. It pushes you in a constant rat race to keep up with your opponents. That is fun, however I think this only works with a narrow tech tree with few choices, where you can quickly research the needed military tech to get equal again with your opponent.
I see where you're coming from and can agree with that, just a little more extra spread would help I think - especially if good special abilities are on techs that don't enable new units (perhaps even less military techs). That way a new base unit isn't quite as good and gives the other research paths viability (even in the military race). Also, this makes experienced units more valuable (something that doesn't work in Civ, because of the far too big spread) - it's just what might be enough to close the gap! So, for example, university has better tech, so they have plasmathrowers - but the spartans and their experienced troops can still win and have good chances, because their experienced units compensate for the tech lead. And upgrading units kills experience - hence it's not always a no-brainer choice, allowing you to either try to tech-race or to keep your units top-of-the line experience-wise, both would be viable strategies.
I mean, there is already a big example of what feels "good" in Planetfall:
The Flamethrower->Plasmathrower->Helion line as native/infantry killers with the InVitro->Cyborg line as no-war weariness line and the marine/droptrooper->mobile infantry line as mobility line. These three paths have a nice spread in strength that you get the feel that you get better units (but not overwhelmingly so, with right strategy even older units can stop better ones, also that might be why I dislike the gravebringer, because it sort of breaks down the whole infantry line thing for me - and make the tech for it a must-have; with several lines, you are more likely to have at lease one line pretty advanced, meaning you are still good in the strength race).
Also, with these infantry lines, you could also make the argument that you could roll them into a single line, differentiated by special abilities - but I think having them split as now and having special abilities to customise them more works pretty well.
Are you sure that faction who were Pleased with you also didn't want to trade tech with you?
I'll double-check later, perhaps there are other things as well.
EDIT: Ah, now I see what Pfeffersack meant: Lal at Pleased does trade now, so it was probably more of a situation-specific thing in my current game. I also think it's because in the vanilla game, it's easier to arrive at pleased as there are more civs - Planetfall has only six factions as possible trade partners and has more tensions between them, making it more difficult to trade (as you don't get them to pleased that often) in comparison to the standard game - I need to break out of these impressions a bit.
Cheers, LT.