I think 2-step approach with overcalling first is appealing in several ways.
A. 2♦ takes away their space. They can no longer distinguish between sound and weakish raise, as they can over double.
B. I am nicely placed if partner introduces ♠ voluntarily:
1♥ 2♦ any 2 ...
@Frances: Back at times, when strong pass was not restricted even in club pair games, at least at my jurisdiction, we had an elderly pair. When the lady opened the bidding, she transferred her 5+card suit or bid any-strength balanced 1♣. Her partner always opened naturally. Quite a ...
Through many years, I have proposed superaccepts after 1N(15-17)-2R onlÿ with 4 trumps and weak doubleton(Ax or Kx possible with control maximum), as suggested by Danny Kleinman (The Notrump Zone). Over the years, such hands only rarely appeared. Today I suggest simple +2 superaccept with good hands ...
1N-2♣ = 54, 55, 64 majors
1N-2N = either 55+ minors or 65+ majors
1N-3♣ = either 6+♣ or 65+ ♦ and either major
1N-3♦ = either 6+♦ or 65+ ♣ and ♥
1N-3♥ = either 6+♥ or 65+ ♣ and ♠
2-suited option is always used constructively.
When playing opener transfer responses to 1♦-1M (1♦ unbalanced), then 1♦-1♠-2♦ shows 5♦4♥, limited values and no reason for 1♦-2♥ being reverse Flannery.
My WJSs are about 5-7 HCP and my constructive 1♦-1M-any-2M are pretty frequent!
With the hand above, 1♥ overcall is quite an option. My second round double surely shows fair hand, more like:
Secretly I hope for 2♠ from my LHO and next double from my vis-a-vis.
I am not overcalling 1N even ...
You probably have a default agreement for transfer to their suit, like:
Might use it here as well.
In the example above: 1♣-(1♦)-2♣ I would take 2♣ as natural ♦. Not a final contract, usually :D.
To overcome 25 IMP deficit, I would need at least 3 reasonable swings. I don´t bet on opps misplay of 4♥, which they will certainly bid. I´m looking for their one off and our 6 IMPs if partner can´t accept the invitation.