Could this work?

Incadescent bulbs have a poor spectrum for plant growing, and would only be good for heat. A spiral compact flourescent would work in your scenario. those energy saver ones probably with a fairly hight wattage (19 watt maybe) with a blue tint, rather than yellow tint.

day light might be worth a try first, only bettas don't prefer to be in bright sunlight (I have read) though I don't know how much it actually stresses them. If you don't mind experimenting to see what works, I go sunlight first. I think the java is low light, right? i am not sure of the other. It should be fine.

As for the fish, 4 gallons is good, with 25- 50% change as you said. make sure the top cover plant doesn't cover so much surface that the betta can't get air of course. the plants should help to keep the water healthier. The sun would heat the water, ideally you want 78 degrees IMHO, but i think the range I have seen is 72-80 is fine. I have noticed more activity from the warmer temps. hte light might help, but I am not sure how hot they get, they are in my ceiling fixtures and I don't often touch them.

As for betta type, I am not familiar with the paradise variety...now I am deciding whether I want to temp myself looking at pics!! I'll want one. A veil tail is cool to and there are a lot to rescue

Also take care that the betta can't accidentally jump out. That is up to you to figure. I haven't really had trouble with this, but I know they are capable.

Hope that helps!

Well first of all if you are planning on using live plants the incandescent lights arent going to work, they dont give off the UV lights that plants need to go thorough photosynthesis. Why dont you just get some silk plant (they wont tear your bettas fins) if you dont want to go the route w/ flourescent lights. You also need to take into account that bettas prefer a temp around 78-82, why wouldnt you buy a cheap heater to keep the water constant or atleast a room w/ a constant temp. I also am partial to Bettas, i only have four right now. 100% water changes are totally bad, but the key is only to do them about once a month rather than everytime you change the water...I normally go w/ a 25%, 50%, 75%, 100% pattern, each representing a week (and if need be a small one in between if the water needs it). But over all the idea not a bad one. But one more question how many bettas are you planning on rescueing like this? If you want to go for alot my suggestion would be to buy a few small 2.5+ gal tanks and put dividers in them to seperate your bettas and there you can add a few more with still ample space *IMO* and now they make small heaters for these small tanks. Let us know how things go.

I think you are on the right track with your idea..the bigger the vase the better...you could theoretically fit in a small round UG filter if the opening was big enough, and add some bubbles for interest...you can buy the full spectrum, screw in flourescents at the pet store...let us know how it goes!