well, either module would eat up a lot of your rack, but my two favorite modules are intellijel's insane shapeshifter wavetable modulator. i'd kick maths out for that, but i just don't like maths to begin with. it's too complex (i like 1 function modules better eg. intellijel triatts for CV control and a dedicated ADSR, but that's me) and i just don't like the looks of it, but it's your rack and it's one of the highest rated modules so who am i to argue?
there are other smaller wavetable VCOs to add some tonal variety to your STO like erica's black wavetable or various mutable instruments modules like braids.
i just learned about pamela's new workout tonight and am really impressed by how it seems to replace both a 4xLFO batumi AND a quad clock modulator. that would add a lot of PROGRAMMABLE clock modulation to your system. in a small system, intellijel's polaris filter offers a huge variety of analogue VCF tone to a system. other modules might do specific tones better, but i haven't heard any analogue filter that can do chunky, juicy, rubbery, creamy AND attitude. maybe a SEM might be a little juicier or a crazy WASP might grunge harder, but they can't do everything else. it's a reasonable 10hp too.
as to envelope generators, i couldn't imagine using anything but intellijel's dual ADSR because sliders just make more sense in an EG to me.
i wish i better understood modulars, especially utilities, so i could help more, but even there like everywhere else, it all boils down to preferences in sound, function & layout.
regardless, i'll argue with ANY expert that shapeshifter & morpheus kick tons of analogue butt in the tone department except maybe they need some grunging up to sound less digital... a good filter and a metasonix tube VCA would help there i'd think. check the demos out for yourself and decide for yourself if anything i've suggested works for you.