An idea to add three (more like two and a half) new elements to the powder toy to enable a whole new range of biological processes and experimentation. These are:
SUGR (sugar)

• powder
• off-white in colour 0xFFFFF9F2
• melts at 459°K if molten SUGR is heated further to 470°K colour changes to to 0xFF9E793 (simulating caramelisation)
• reacts violently with ACID to form COAL, WTRV and heat
• soluble in WATR and DSTW to produce SUGW

SUGW

• reacts with ACID in a similar way to SUGR
• QRTZ can be grown using SUGW as well as SLTW
• boils at 400°K to form WTRV and SUGR

Biology:

• stickmen can eat sugar and drink sugar water to regain health

YEST:

•  no longer sinks to the bottom of a water tank, but lies suspended in it
•  eats SUGR and WATR, excretes CO2
•  can displace water when growing
•  is killed by SALT and SLTW

PLNT:

•  EDIT: will  grow into WATR the same way as normal
•  will grow into SUGW twice as quickly as into WATR
•  photosynthesis:
•    will not perform a direct conversion of SMKE/CO2->OXYG
•    PLNT now acts as a catalyst in reaction SMKE/CO2+WATR/DSTW+PHOT->SUGR+OXYG
•    EDIT: PLNT can be supplied with water from a "pipe" made of WOOD
•    or in solution BUBW+PHOT->SUGR+OXYG

When PLNT isdirectly adjacent (non-diagonal) to another pixel of PLNT or WOOD:

PLNT can work as a whole system i.e. can recieve water in one location, SMKE/CO2 in another and PHOT at a different point again and reaction will still take place, releasing O2 at location of SMKE/CO2. WOOD can be used to absorb water

PLNT, YEST and WOOD now have a sugar storage capacity (stored in tmp2), converting pixel of PLNT into VINE when tmp2=3 (more plausible growing mechanic). PLNT and YEST will remove SUGR from SUGW to produce WATR and increase tmp of YEST/WOOD/PLNT

When isolated (can be touching diagonally) from other pixels of PLNT PLNT will directly output SUGR if supplied with correct reactants

yes I know :( but regardless, the gains in complexity and interest outweigh the disadvantages of save-breaking. Most problems can be easily remedied using systems of WOOD and PLNT

okay I changed my idea to be more backwards-compatible