The amount of effort it'd take to shove in an extra clan that isn't participating is far too big for no reason at all. Felidae is still an alt clan, and promises to be so for a long time (clan does zero recruitment other than forums (low results, if any) or alt accounts).
For Felidae to be even valid to participate in RPCL, first off, you have to fix that.
LOL if we really want it we can just swap some mains into Felidae temporarily for RPCL3.
That's a pretty obvious exploit, one that (thankfully) no clans in RPCL used so far to cheat scores - trust won. RPCL's goal is not full-fledged competition, but to allow players in RP clans to have a taste of competitive gameplay without hindering their clan's main CL score (see: CORP/TJC's rosters).
If trust isn't enough to ensure clans will legitmately bring in RP-based players who want to step into the competitive world, then changing the ruleset in order to avoid it will be needed, and you'll effectively only delay/damage RPCL3. So, please, don't have us need to leave the trust-based zone.
In fact, that's why we don't allow alts in - because we don't want the many, many exploits to get competitive-based players joining in and ruining the purpose of the competition. Since wouldn't find a way to allow them without opening up many exploits, we just didn't allow any, at all, hurting players who do diplomacy and strat on different accounts, as well as those who just have an alt they use as much as their main.