Ok,
Look at it this way, there are many advantages to having summoning, but there are also a few disadvantages.
The pro's of summoning are...
1. If you get 40 or 52, you can use summoning pouches and scrolls to help you while you do quests, skills, etc. where running is helpful. (40 for Bull Ant, 52 for Terrorbird)
2. With summoning, you pets, which are pretty cool, but overall sort of useless.
3. You can put those charms you may or may not have collected over time.
Some of the cons are...
1. Your combat level might mess up your Bounty Hunter situation, I'm not fully sure about this.
2. It could potentially ruin the account's value, again not 100% sure, just came up with these.
3. The time it takes to gather the charms for summoning could be a pain in the ass, unless you like doing slayer or charm hunting.
4. You might have to spend 1m+, and unlike the guy above who only spent 700k on 52 summoning, I spent around 2m on 52 summoning, and it took a hell fo a long time to get the charms, be it because I didn't go charm hunting or whatever.
Now, don't just look at the 3 pros and 3 cons and decide not to do it, summoning has been extremely helpful to me in the past. Instead of spending thousands of coins on one super energy pots, which only restore a total of 80 (per pot), I can spend 50gp for Terrorbird to restore me 30%. Also, Tireless Run scrolls (the scrolls for Terrorbird) are stackable, so, if you bring a summoning potion and a few pouches, you have unlimited run energy. Woot.
On the other hand, summoning could ruin your Bounty Hunting, as it might put you up a crater, which would suck. The summoning wouldn't really do anything in Pvp Worlds, as your level is (Combat+whatever). This, strangely enough, could work to your advantage as some people might assume your a main/beginner, as most pures do not have summoning.
Overall, summoning could be a good thing, and a bad thing. It really depends on the way you look at it. Summoning would make your pure quite original, but it also might be a bad kind of original.
Your decision. Make sure you have all the charm for whatever level you want before you start, because you'll be really frustrated if you get to around 30 summoning, then run out of charms and don't like charm hunting.
Just make sure you look at all the sides of this before you go for it.