Resin coating cement panels - Cracks or Softness

The challenge I have been debating between epoxy and polyester resin goes on. I have been casting brick panels in cement with a variety of mortars, cements and grouts to get a surface that resembles brick and can fill the backside of some frames. I like the idea that the cement will resist the deteriorating effects of water more than the plaster gypsum products I have been using, but the cement has been slower to work with and is easy to damage while it is drying. I have gotten a set of 10 or so panels and felt they needed to be coated to resist weathering and to create a more finished looking piece. My product of choice has been epoxy, but the expense and time it takes for epoxy to set isn't desirable. Also the epoxy I have been using tends to get soft with heat and as a result it seems less desirable for outside conditions where I can't necessarily control the temperature. The bond of epoxy seems strong to wood anyway, but if it becomes soft then there is room for problems like keeping the shape that it may form into to if a piece is suspended in a random way. Then if there is rain or dirt it would puddle or build up in those sunken or raised areas, so the epoxy I am using is not the right choice for this application. Also I had some left over polyester bonding resin available to use. My biggest concern now is the adhesion to the cement. I wrote an review and commented on some of my issues here on Live Action News - The Salt of the Earth and at least feel some satisfaction in that the larger scale engineering technology of the concrete industry is dealing with some of the same problems, but on a much larger scale. Without reinforcing the panels I have gone on to apply a thin painted layer of polyester resin with some fillers and atomized steel particles to resist weathering and create a rusted finish. The polyester resin also feels thinner than the epoxy, so I am hopeful that it will seep in better than the epoxy would. Still over time there may be problems with cracking if the cement continues to shrink, after the polyester resin has set. The coating may absorb heat if I use the panels in the sun, because it is black, but the interior of cement should resist allowing the heat to pass through to the interior of the structure. This should be better than a solid epoxy or polyester object that could allow the heat to pass through. I suppose that I could just use a cement paint to cover the cement, or a specially designed epoxy paint like those used to do floors in car mechanic shops, but the resulting high gloss finish isn't my thing. I think the other problem here is that I like some visual weathering effects like rust, but don't like structural deteriorating effects like cracking and crumbling. Time will tell. Now I want to send these pieces through a gauntlet of test for weathering, like suspending one in salt water, coating one with acid, leaving another out in the sun, burying one in the dirt with worms and grubs, freezing one and burning one, just to see what happens. Burning may not be a good idea, but the other test for durability will work.