I think LMMS should get better internal VST and samples. Even if actual plugins aren't bad, they could be better. Also people that want to use guitar and pianos or other instruments have only some not so good samples. I posted this because i see that internal plugins are one of the main reason about because people use FL Studio. Also famous people, for example Martin Garrix, said: "I use a lot of FL Sudio plugins". So i think, as LMMS made for Zasfx, they could ask for some minor free plugins. For example Project16 Slap Bass and Acoustic Vince aren't so known, but they are good, easy-to-use and not so heavy, and maybe Project16 could let LMMS developers implemented them in LMMS. For piano maybe you could get mda Piano or Safwan Matni General Piano

Another thing is that LMMS should really get an internal Sampler like Image-Line DirectWave, One Small Clue's Grace, or TX16WX Sampler.

Other VSTs good but not heavy
Strings: Matnitron
Saxophone: DVS Saxophone
Flute: Ixox Flute
EPiano: Gluereeds
Organ: Combo Model V (even if i think organic is one of the most cool LMMS plug)

About internal effects i see your working for them :)

I think LMMS should get better with vsts like these as internal ones, but maybe is only my opinion.
Oh , and also some cool light vst are Stringsynth and Stringer