The height difference was a major problem in the first game, but Mk2 fixed that. It doesn't matter what leg parts your Shinki is wearing. As long as the aim and angle is correct, the weapon will hit.
Set pieces for Shinki-specific RAs are important because they force you to think about how to balance that power and get past the obstacles that it poses. It may be restrictive, but it works. Since a set doesn't encompass all the equipment slots, you can work on adding extra parts within the cost limit. Pick your best weapons, add accessories that enhance Shinki strengths and/or compensate weaknesses.
In Ianeira's case, her base equipment's high cost level is part of her identity as a Shinki. After all, an overdressed mermaid won't really be much of a mermaid.
The people in Ad-Hoc Party are about as colorful as the Shinki they use. It astounds me sometimes how some people can use seemingly unwieldy weapons effectively (like Grenades, Floating Mine Sprinklers and Particle Blasters).
Personally, I prefer to stick to an orthodox setup. One light gun (pistol/rifle) for mid range, one small sword/knuckle for CQC. and a launcher for long range attacks.
My love for Harumi goes THIS far. Accomplished 2012/08/17.