There’s a glitch that can come up with stacking templates: three +1 ECL templates are not necessarily equal to one +3 ECL template – either in standard d20 or in Eclipse.
In standard d20, that’s because of unexpected interactions and because assigning ECL modifiers to templates is basically guesswork. You could wind up with something pathetic or with something seriously overpowered depending on just what you do.
In Eclipse it’s because ECL’s only increase by +1 for every full 32 CP – so three +1 ECL Templates, built on 56, 48, and 63 CP come out to 167 CP – equivalent to a single +4 ECL template. It could be as high as 189 CP – equivalent to a single +5 ECL template.
Pure Eclipse point-buy characters don’t have to worry about that sort of thing though. If they want to have special abilities derived from their ancestry or exposure to weird radiation or some such thing, they just go ahead and buy them. If they want something that usually goes into a template, they put it into their racial build, and go on from there. After all, you can grab power-packages from racial builds just as readily as from any other source. In effect, truly pure point-buy characters usually don’t normally use Templates except as shortcuts.
It gets a little more problematic when you go for the classical method and simply slap on a full template and apply the ECL modifier.
Still, even for Eclipse characters, stacking one template and one race can usually be assumed to fall within the margins of error. After all, the +1 ECL in a Template doesn’t include intelligence-based skill points, or the enhanced skill and ability limits, or any other “level”-based effects, so it’s not quite as good as a level – and it’s rare for everything in a template to be optimized for a particular character, so even if they wind up a few character points ahead on the deal, it’s manageable. For example, the ever-popular Half-Dragon Template is worth 115 CP, while three levels are only worth 72 CP (24 CP/Level) + 24 CP (the cost of three d4 hit dice) + (3x Int Mod CP for SP), so the character could be gaining up to 19 CP on the deal – if you disregard the enhanced skill, ability, and base level components and the character doesn’t already have something that doesn’t stack, such as low-light or darkvision.
Now, if you’re letting people design and use their own Races and Templates, it’s best to insist that they put everything into their racial setup, It keeps the points balanced.
Beyond that point, it’s best to apply the following rules:
● Player Characters may only have one Race, one basic Template, and one Party Template – although they are free to expand on either the Race or their Template and move up the ECL chart or to buy abilities from other races and templates.
● Companions and NPC’s rarely need to be handled in as much detail as the player characters. If the game master wishes to do so, simply add up the costs of any templates applied to them normally. If the game master doesn’t want to bother with that, then they can have multiple templates – however, they’re subject to an extra +1 ECL modifier if they have two or three Templates and to an extra +2 ECL modifier if they have four.
● If a Companion or NPC has more than four Templates, the game master is out of his or her mind.
It’s worth noting that Eclipse races can be used as templates for classical-style characters. There may be complications with the ones that have overlapping features, but in most cases it’s straightforward enough: simply add +1 ECL to the adjustment for the race in question and now it’s a template.