The problem with seating as people buy-in is knowing, in advance, how many tables will be needed. In other words, if you've got 5 tables of 10 seats, and people begin to buy-in, can they be seated anywhere? What if, after everyone buys-in, you've only got 25 players, and hence only need 3 tables? Kind of sucks if you've got the players already spread out over 5 tables.

The point is, you don't know how many tables you need until you know how many players are playing. I don't know how Bally's does this. I guess you could spread players out over all of your tables, and when you're ready to start, move players seated at the unneeded tables to empty spots on the needed tables.

So, if you don't know how many players will be ultimately buying-in, or who those players are until they buy-in, you are kind of stuck with the method of buying them all in and then seating them all at once, IF you want to have random seating. Otherwise, seat them one at a time and they'll end up at tables with the players close to them in line.

If you do know at least most of the players who will be buying-in, you can pre-buy-in players and then mark them Paid In Full as they actually pay you. This works best if you have a regular tournament where a good portion of the players are regulars. Buy-in everyone who usually plays ahead of time. Seat them. Then mark them Paid In Full as they pay you. When all is done, remove players who didn't show. Then balance the tables.