I have attempted to attach to attach different cells and multiple cells to battery boards in the past, and I certainly recommend against doing so. Every time I attached the new batteries, the board would die after some usage.
Another reason to not use these portable charger boards is the amount of mod work that needs to be done to them to integrate them into your portable design. Most of these boards have annoying "key" switches that you need to bypass or integrate in some manner, and you also need to remove the usb ports and rewire them to other locations in your portable. If the board has a flashlight led, you need to remove this as well, and the charge indicator leds must either be rewired or mounted along with the board in a particular manner in your portable. Additionally, many of these boards have an insufficient current output or multiple outputs that can't be tied together.
What you really need is a three board solution. 1st, an universal output board that can supply sufficient current (found
HERE). With this board you can connect any number of batteries (in parallel) and the board will always work. 2nd, an universal charge-only board (found
HERE). Like the first board, you can connect any number of batteries (in parallel) and the board will always work. 3rd, a low battery indication circuit (diagram found
HERE). Is this three board solution more expensive? Will it take up more space in the portable? Yes, but you can use all the batteries you like, and wire up a proper charge-or-play or a proper charge-and-play circuit, while having sufficient current for just about any portable.