Really, in my experience, there is no way to get rid of the wrinkles. If you really are in the situation where you are going to replace it because it is so bad, you might want to try making a rigid frame for it and stapling the screen material to the frame. This may cost you about 50 bucks in wood, but could do a nice job if you are careful.
The least expensive good theater screens really are the permanently tensioned ones as they come with a frame that keeps the screen tight and is designed more for home theater use than rolling up and being inconspcuous.
Good tab-tensioned screens typically cost upwards of 1000 bucks (easily) for a 16x9 screen. Don't know if they sell them un-motorized, which will bring cost down a fair amount. But, tab-tensioned is the way to go if you have to roll it up when not in use.
Electric masking is VERY expensive for full-on masking but is available. You can also get masking that is electric that specifically comes down to convert from 16:9 to 4:3 and back. Check one of the major screen manufacturers for pricing. Tab tensioned plus masking in an electric screen... I would expect nothing less than about $2,000.00 if you are lucky.