If we do not get diminishing returning the way bonuses work needs to be changed. At the moment it's better to fit more of one module and rely on a support robot for things like sensor amplification or energy or repair.
This means that for PvE the best thing to do is have a combat doing pure damage and a support robot helping.
If we're allowed to stack almost any module like we can now the bonus should be linear and not apply the new bonus to the old bonus. This is reducing complex fittings. If I could only fit 2 tunings but have them more powerful than current tunings I would then be able to choose something else to fit.
This is very different from PVP where you have to focus on range and tanking rather than DPS but for PvE it's very boring. PVP could be spiced up with either module limiting (I am against this) or very small bonuses from more than 2 of the same modules. First module gives one bonus, second module gives more bonus, third module gives almost no bonus, 4th gives nothing.. etc.. (I support this ONLY if all bonuses get a increase in strength)