Here are some stuff that just came to me one day:

Unstable Isotopes (or ISTO):

ISTO is a lilac-colored gas.  It can be made by mixing DEUT and EXOT (that is not in it's cloning phase), or by mixing ISOZ/ISZS and BIZR/BIZS/BIZG.  Upon contact with OXYG, it turns into neutrons and pressure the same way DEUT does with neutons or LIGH (but not THDR, apparently).  ISTO, when hit with a photon, splits into one HYGN and two neutrons.  It turns into SING under pressure of -100 or lower; this is a much easier and more reliable way of making SING than proton collisions because making SING with proton collisions is nearly impossible and usually only done by accident; making SING with proton collisions might just be the hardest reaction to achieve in tpt, but I digress.  Under pressure of 200 or higher and newtonian gravity of 200 or higher, ISTO turns into one of two possible elements;

If Newtonian gravity(200+)>Pressure(200+) then ISTO becomes BHOL

If Pressure(200+)>=Newtonian gravity(200+) then ISTO becomes NTRS (see below)

ISTO is the only gas that's unaffected by air velocity, meaning air cannot move it but can still pressurize it.

Neutron Star (or NTRS):

NTRS is cyan, but glows azure in fire display.  It has some of the properties of an energy particle and also some of the properties of a solid.

Energy particle properties:

It glows (as previously mentioned), is immune to VIRS/VRSS/VRSG, and is trasparent to powders and liquids.

Solid properties:

It can't move, is undying, and has the a stack limt of 5.

Endothermic creation and containment requirements:

When ISTO (see above) turns into NTRS, the resulting NTRS is at max temp, just like brush-spawned NTRS.  NTRS turns back into ISTO when pressure and/or newtonian gravity is less than 200.  If newtonian gravity exceeds pressure then NTRS will become BHOL.

Electromagnetic field:

NTRS absorbs electrons and it's tmp2 goes up by 1 for every electron it abosrbs.  If it's tmp2 is greater than 0, it becomes a magnetar and will spark any IRON, BMTL, BRMT, and TUNG within a square radius equal to it's tmp2.  The maximum radius is 25; electrons will pass through instead of being absorbed at this point.  While in it's "magnetar" phase, it can also absorb protons and it's tmp2 goes down by 1 for every proton it absorbs.  When it's tmp2 reaches 0, it exits it "magnetar" phase; protons will pass through instead of being absorbed at this point.

Heavy elements:

NTRS absorbs neutrons and it's tmp rises by 5 for every neutron it abosrbs.  If it's tmp is greater than 0 and when pressure and/or newtonian gravity is less than 200, then instead of turning into ISTO, it turns into one of the following elements depending on how high it's tmp is.

If tmp is 1-20, then NTRS becomes molten GOLD

If tmp is 21-40, then NTRS becomes molten PTNM

If tmp is 41-60, then NTRS becomes molten POLO

If tmp is 61-80, then NTRS becomes molten URAN

If tmp is 81-100, then NTRS becomes molten PLUT (molten PLUT produced in this way doesn't solidifiy into STNE)

A tmp of 101+ will also yield molten PLUT, but as tpt continues to mature and more new elements are added, tmp values of 101+ may yield new molten elements instead.  This method of making GOLD will make GOLD factories more feasible; curing molten ROCK to produce only GOLD is a lengthy and difficult process (pressure also tends to fluctuate, so you can be left with unwanted QRTZ); This newer method of GOLD-making can be done in a fraction of of the time.

NOTE:  If you hadn't guessed by now, ISTO simulates tritium.  Since NTRS is immune to virus, we should also make SING and BHOL immune to it; The wiki says that SING and AMTR are immune to virus and while AMTR is, SING isn't.  And while tpt isn't supposed to be completely realistic, the idea of such powerful things like black holes and singularities being vunerable to something as simple as a virus is downright ridiculous.

1 in 12500 chance also means it takes too long, especially with large containers full of molten ROCK; this newer method can make GOLD in a fraction of the time, as mentioned above.  Also, synthesizing EXOT is not so hard with PTNM, but you can also use ISOZ/ISZS with BIZR/BIZS/BIZG.

You can use CLNE to make elements that aren't made by reactions; like ACID, GLOW, and GEL.  And I have a compact machine that easily makes EXOT quickly:

And the DEUT and EXOT(not in it's cloning phase) just have to touch each other to become ISTO. I do, however see your point about high gravity; maybe the NTRS can be so it doesn't change back into ISTO and instead turns into those molten element when cooled down to 6000C.

I need to clear some things up.  Every production chain has to start somewhere and raw elements (elements that can't be made via reactions) are a good element to start with with, because they can't be made by reactions anyway--not to say all factories should start with raw elements.  But wheather you start with raw elements or not, you have to use clone variants in order for your factory to run continuously and without intervention.

ISTO turns into BHOL if newtonian gravity is higher than the pressure, or into NTRS if the pressure is higher than the newtonian gravity; both the newtonian gravity and the pressure need to be at 200 or higher for either of these reactions to work.

I never said my EXOT-maker was the smallest or most efficient, just that it was small and efficient.  I also made an even smaller version today:

This is, undoubtedly, the latest in Cold EXotic Matter Synthesizer (or CXMS) technology.

We could make the gravity threshold lower then, or you could just use GRAVITY WALL.  You can't make photons into anything but SPRK or other energy particles.  As for SPNG duplication, the only way you could be doing that is with DRAY--no reactions make SPNG.  I didn't think I would need to specify that you can also use CRAY or DRAY to make raw elements; making things with CRAY or DRAY is also not a reaction and, with BTRY or CONV(SPRK), is functionally the same as using clone variants.

EDIT:  I saw the SLTW machine in the project and saw no CRAY or DRAY, or anything to keep that SPNG from running out of liquid.