Yes, actually, you can still play nearly exactly how you describe it.
It's not advertised on the website, but it is not an exploit, either.
No matter the current level of your character, you can play using a free subscription
if you only have one active character. Any side-characters need to be archived before the option to use Free Access pops up.
The limitations of Free Access are:
- One active character only
- No EXP gain unless you are level 15 or below
- Any characters above level 15 cannot take new or finish any current quests
However, you can still log into any lvl 15+ character to talk, play, fight, loot, and so on.
As for a buy-to-play system, it's been suggested many times. To my knowledge, the primary issue is that Istaria cannot sustain itself off of new buyers only and it has too small of a player base for micro-transactions to sustain the game's costs beyond that.