I have a male betta in a planted 10 gallon, with two female balloon mollies, two female platties, and a school of eight neon tetras, and 1 guppy. Temperature is at a constant 78F and I have a HOB filter rated for 10 gallons running on it.
The most aggression has come from one of the mollies, and that was to the other molly and platties, not the betta, nor the ghost shrimp that used(!) to be in there. All of them would chase the 3 guppies I had in there originally, but that stopped, now that there is one and he's been in there a while. I added the eight neons a couple weeks ago, and they are doing fine.
When you say suckerfish, you probably mean a common pleco, which will get way too big for a 10 gallon, even a 20. There are other types of plecos that may fit into a 20 for life, I don't know for sure. Anyways, the only cleaning they would do is eat algae on your glass or plants, unless you supplemented with algae wafers/drift wood/whatever he would probably starve to death. As for 'algae eaters', Chinese Algae Eaters only eat algae when they are young, and then move onto plants.
As for bettas, it's said you can house a male with two(maybe more) females, and a 10 might work for that if you have enough hiding places. If you have multiple females, you'd need three or more otherwise there will be deaths. That all depends on the temperament of the fish anyways, you may get one that can't be put with anything and end up with dead fish anyways.
Good luck finding a good stock list, I know it can be done, you just need to research what you want to put in it(required temp, food, aggression, schooling, max size, ...)