This has been debated and even implemented in the past when @Kim and I managed CSGO ZE. As well, I think this was brought up once or twice when CSS ZE was our pride and joy. As our NA CSGO ZE server was #1, we added an EU server as an exact copy, but it never really took off despite our efforts. Maybe it was bad timing or maybe people weren't interested and would rather play in the more populated server. Having a single server seemed enough for us at the time. We offered a "premium" product that drew players in. They'll gladly wait for someone to leave until a spot opens up, as I and many have done. If you don't want to wait, it encourages donating to get a reserved slot.
-Allows players to still play, despite the main being full
-Puts GFLs name out there with the possibility at getting in the top 5 ranked servers Cons:
-Could split the existing community and impact population
-Favoritism could spawn as a result of the split (not necessarily a bad thing, but worth mentioning)
-Could stress out existing server staff as they try to find new members qualified to staff the server
-Could impact our #1 position
Of course with the implementation of F2P, it allows a wider availability to everyone so its an obvious win, but there's a possibility for a very rocky start that could cause some of the cons I mentioned down the road (maybe not).
I'm not really for or against it, but I thought I'd offer some insight.