Cordylines, unlike say oak trees, don't actually increase very much in size simply because they get higher. Rather, the crown of the plant mainly gets further away from the ground without getting very much bigger - well it does get a bit bigger but nothing like on the same scale as typical trees. Remembering that it is leaves rather than wood that places the main demand on the metabolism in the roots, we realise that the metabolic load the roots need to service for a Cordyline of a given height in comparison to typical native tree is much, much smaller. So they need much smaller root systems than those native trees. So they aren't going to present any subsidence risk. True palms are similar. I've planted a Chusan palm (Trachycarpus fortunei) - which incidentally is rather more cold tolerant even than a Cordyline - right next to my house and I'm not bothered.

You are actually quite lucky still to have a full-height Cordyline. Most people had theirs involuntarily cut back to ground-level during winters 2009-11.

Cordylines do sometimes resprout from the trunk rather than from ground level. I have seen damaged cordylines with large numbers of new shoots at various levels up the trunks. Typically, though, many will abort, unless you are fairly quick about rubbing out the ones you don't want and encouraging the ones you do want. I think these new trunk shoots are more likely to happen if you just remove the growing tip, rather than make a major shortening of the trunk. So a possible strategy is to cut out the growing tip, retaining plenty of leaves, and see if you get any new shoots part way down the trunk. You could then rub out the shoots you don't want, and later, once the favoured shoots are well established, cut off the trunk off just above the shoots you wish to keep.