[quote]I think the issue really comes down to whether you want to focus on mechs in a hard science fiction (i.e. sort of realistic or plausible) or soft science fiction (i.e. science is magic) type of way.

Machines that move like humans (in regards to agility/dexterity) and machines that can be customized, upgraded or retrofitted without great difficulty (ignoring the difficulty of making changes to standardized designs) to me at least falls a bit too far into the "science is magic" category of settings.
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Mecha are pretty soft SF anyway; walking combat machines aren't really particularly practical and plausible, and take more than one 'handwave' of reality to make them anything even approaching practical. 
Some kind of invented material or power source usually, to allow them to exist. With most Gundam series it's the invention of a new power source or type of construction material, and it's the same in most other settings as well - Battletech/Mechwarrior (whatever) has the Neurohelmet and Ferro-Fibrous Armour, as well as miniaturised fusion reactors. Heavy Gear has it's own similar things, as does pretty much every other mecha-based setting. Everything else is completely stylistic choices; in the first Battletech novels before the 'feel' of the universe was completely nailed down, the mechs did actually move more like those in most anime; doing combat rolls, dives and such. It was only after more of the books came out that they became the slower-paced 'walking tanks' everyone thinks of now.  

It's all a matter of personal taste, and it's obviously up to Aristo which we go for. Personally, I'm hoping more of the anime Real Robot side, because that's more to my taste. Whichever it is though, we should probably ensure its' consistent between all of us.