Top access under a table could be a problem, yes. Is your Savic Plaza in use? I'm guessing it is. But also it sounds like you want something solid sided. Yes if she's climbing the bars she might fall. It's hard to find any tank style cages with a front opening door though. The idea of two bin cages with a front door sounds ok. Could the Plaza go under the table instead, so you could have something like a maxi duna on top of the table? I got a console table thing especially for fitting two Plaza cages - one on top, one on the shelf underneath. The underneath one only works because it has a front opening door and there's quite a bit of space between the bottom cage and the top - but not enough to fully open a top door.
When I had the Barney and one plaza, the Barney had to go on top for that reason.