Short odds don't necessarily mean poor value, but, in order to make any significant return, you either need a massive stake, or, as the OP is proposing, combine a number of them together. Unless you are, on average, finding +EV (an increasingly more difficult proposition as you increase the number of bets), you will just multiply the bookie's advantage.
Also, obscure and illiquid markets are more likely to present arbitrage opportunities.
The problem with arbitrage, as you note, is that you have to have a big stake, have the appropriate software and the time to devote to it. Anyway, I think bookies are now on to it and are making it harder and harder to win.
You're correct in saying that the bookies love multiples - the more the selections the better as far as they're concerned. I think their favourite bet is the Yankee. One selection goes down and that's 7 bets lost.
The advantage the OP has over the traditional accumulator is that he can cash in at any time and take his winnings. He doesn't have to go all the way to the end. Generally that's not possible with an accumulator although some bookies offer an on-line cash in facility (with the odds again stacked in their favour).
IMHO punters would be far better devoting what is a relatively short amount of time searching out the best odds for their particular bet. It's amazing the number of people who only have an account with one bookie but it's not unusual to see a 4,5 or 6 point difference between the best and worst odds on a football treble.
As for value, in the absence of a rigorous statistical analysis (which I haven't got the time or knowledge to undertake) I use a gut feeling having watched football for 40 plus years, plus league tables and form. I can look at a coupon and see which teams I think are overpriced. Not always right but I've had a fair share of success over the years, although probably still down overall.
Conversely, I can look at a game and identify teams that I think are underpriced - the Premier League is particularly bad in this respect, certainly compared to say League 3, and so I tend to avoid it.
For example, City were quite short odds to win at Villa and I think Chelsea were odds on to win at Stoke despite their poor form. Many punters would have had them down as "bankers" in their accumulators.
La Liga too. Real Madrid were odds on to beat Sevilla on Sunday and most people, forced to have a bet would have backed them. They lost 3-2 after leading 1-0.
Imagine how you would have felt if you'd backed them in-play at incredibly short odds when they were winning!